Changes in titratable acidity, viable cells and sensory properties of curd yogurt during lactic fermentation in milk added with mugwort extract have been studied. Milk added with 5%, 10%, 15% or 20% of mugwort extract was fermented with single or mixed culture of Lactobacillus bulgaricus and Streptococcus thermophilus for 24 hours. Addition of mugwort extract markedly stimulated the acid production and propagation of lactic acid bacteria. Among the organism tested, the mixed culture of Lzctobczcillus bulgaricus and Streptococcus thermophilus produced the highest amount of acid, and Lactobacillus bulgaricus showed the highest number of viable cell counts. Sensory property of curd yogurt added with mugwort extract was evaluated as better than reference sample(milk yogurt). The sample prepared by fermenting milk containing mugwort extract at 5% level with Lactobacillus bulgaricus showed the most favorite characteristics.