This is an initial work on a research project which will ultimately test a battery of hypotheses relating to the drivers of consumers’ willingness to buy of Vitamin C OTC. This initial work outlines the product category, the market, and presents the initial theoretical framework to be investigated. Dietary Supplement constitutes a very significant business market in Thailand. Consumers in Thailand consume dietary supplements on a daily, continual basis to supplement their daily dietary intake. More importantly, they consume them as a preventive measure to off-set an environment of ever growing pollution, pressure to perform and stress. The market for dietary supplements is growing, and firms operating in this market are interested to understand the factors and variables related to consumers’ willingness to buy on these dietary supplements. Consumers can also benefit from research insights as the consumption of dietary supplement is not without criticism (e.g. Braun et al., 2009; Timbo et al., 2006). Food supplements or Dietary supplements (EU1) is the official designated term for this product category in the United Stated of America (U.S. FDA 1994). Thailand (ACCSQ-TMHS, 2006), are classified as food products containing micronutrients and its intention is to supplement the normal diet (Greger, 2001). According to Kearney (2010), consumers have increasing levels of focus on the importance of health, which the increased focus on health coincides with an increased availability of health information, which in turn is fueled by the underlying demands of an aging population and an increase in lifestyle diseases. In the EU, the use of supplements is widely practiced in the general population. Statistics reveal that 47% of German women and 41% of German men regularly take supplements consisting of vitamins, and minerals (Reinnert, Rohrmann, Beckers & Linseisen, 2007). The sales ratio in the Thai market between general nutrients and vitamins is approximately 55 to 45 percent. According to the latest IMS Health Thailand report as of end September 2013 (see Table), it is noted that in Thailand alone, the domestic consumption of general nutrients and vitamins as food supplements has increased by more than four folds from 2004 to 2013 (Thai Baht 1.27 billion in 2004 to 5.46 billion in 2013). The majority of this increase occurred from 2011 to 2013. Most of these products are imported from the US. Other major producers and exporters of these products are Ireland, France, Switzerland, Japan, Netherlands, Germany and Australia; whereas Japan, Philippines, Singapore and Vietnam are major exporters of raw materials into Thailand for further refinement (Arunanondchai 2007). In Thailand, exercise used to be the main way to achieve a healthy life. There is, however, a growing belief that healthy food and food supplement consumption is important to be healthy. The present project studies the use of Vitamin C as an example of a dietary supplement, which is widely consumed in Thailand. Vitamin C (L-ascorbic acid or Ascorbate) is the generic descriptor for compounds having antiscorbutic activity. Most animals can synthesize Vitamin C from D-glucose but humans and other primates, together with guinea pigs, fruit bats, some Passeriformes birds, some fish and some insects, are exceptions. Vitamin C is a reducing agent (antioxidant) and it is likely that all of its biochemical and molecular functions relate to this property. In humans, Vitamin C acts as an electron donor for eight enzymes, of which three are involved in collagen hydroxylation (including aspects of norepinephrine, peptide hormone and tyrosine metabolism) and two are involved in carnitine biosynthesis (Dunn et al (1984), Eipper et al (1993, 1992), Kaufmann (1974), Kirirkko & Myllyla (1985), Levine et. al, (1991), Procop & Kiviikko (1995), Peterkovsky (1991), Rebouche (1991)). Vitamin C is sold through various distribution channels, including the over-the-counter (OTC) market in Thailand with limited restriction from the Thai FDA. OTC drugs are medicines that may be sold directly to a consumer without a prescription from a healthcare professional, as compared to prescription drugs, which may be sold only to consumers possessing a valid prescription. The term OTC may be somewhat counterintuitive, since, in many countries, these drugs are often located on the shelves of stores like any other packaged product. In contrast, prescription drugs are almost always passed over a counter from the pharmacist to the customer. Some drugs may be legally classified as over-the-counter (i.e., no prescription is required), but may only be dispensed by a pharmacist after an assessment of the patient's needs and/or the provision of patient education. In many countries, a number of OTC drugs are available in establishments without a pharmacy, such as general stores, supermarkets, gas stations, etc. Regulations detailing the establishments where drugs may be sold, who is authorized to dispense them, and whether a prescription is required vary considerably from country to country. To simplify, any medicine that can be sold over the counter for symptomatic relief of minor or self-limiting ailments without the prescription of a registered medical practitioner is an OTC Medicine. OTC Medicines differ from Prescription Medicines in terms of Margin of Safety, Advertising and Distribution. The project will address a combination of both intrinsic and extrinsic driving factors in pharmaceutical products, including vitamins that can potentially lead to a better and clearer understanding on how consumers perceive the product quality, get influenced by expert opinion, and manage perceived risk when deciding whether or not to buy. Three potential drivers will be investigated in this project for their impact on willingness to buy: Country of Origin image, brand image, and expert opinion. Further, the framework suggests that the relationship between these three drivers and consumers’ willingness to buy is mediated by their perceived risk. Basing on the requirement of developing a theoretical framework to answering these questions, it is foreseen that both practical and implicative results derived from the OTC pharmaceutical market can complete the answer from an experienced consumers’ perspective, therefore this study is adopting the questionnaire set methodology to survey among Vitamin C consumer who are experienced with this dietary supplement. Aligning the survey in respect to prior authority research, the measurement items in this survey were adapted from pre-existing scales of operationalization. A questionnaire will be constructed to assess 5 main constructs. They are: 1) Product Country Image 2) Brand Image 3) Expert Opinion 4) Perceived Risk 5) Willingness to buy. These 5 constructs constitute the main proposed conceptual model. All constructs in this questionnaire use a seven-point Likert scale. The research will draw on existing definitions and measures adapted from the consumer behavior and marketing literatures. The theoretical framework and related hypotheses will be tested using primary survey data by using a statistical analysis software package for interpretation and conclusion of findings. Questions for Product Country Image were operationalized and adapted from Roth and Romeo (1992), consisting of four items. Questions such as “How would you rate innovativeness of Cosmeceuticals products from Country of Origin” were specially designed to capture consumers’ perception of products based on their imaginative association of a product to a country. Brand Image, comprising of five items, is borrowed from Robert (2004) and Cho (2011) which are semantically designed to capture meaningfulness of brand perception to the end user. An example of a question is: “The brand adds value to my life”. Four items are asked in the Expert Opinion segment in order to analyze the pedagogical impact of experts’ persuasiveness, operationalized from Aquevegue (2006), such as “The opinion of the experts about the product is (very good to very bad)”. Perceived risk, being measured by 5 statements such as “You want to enjoy better health” in the degree of respondents’ view is heavily adapted and modified from Chang (2007). This segment is directly engineered to identify and understand expectations associated with products from a consumers’ viewpoint resulting in final purchase action. Such expectations can be understood as benefits or the avoidance of threats that are realized through consumption. Applying the hierarchy of needs model (Maslow 1954) could help to reveal and orchestrate consumers’ purchase motivations resulting in valuable marketing insights. Finally, the construct of Willingness to buy, consisting of five items such as “The likelihood of purchasing Cosmeceuticals is (very low to very high)”, is adapted from Dodds and Monroe (1991). Overall, we expect the results of this project to illuminate our understanding of how perceived risk influences consumer decisions in the dietary supplements market. Specifically the results should shed light on the effect of three key drivers of perceived risk, as well as of a key outcome of perceived risk.