The review of previous studies on interlanguage pragmatics reveals that they have been modelled on cross-cultural pragmatics. However, in order for interlanguage pragmatics to contribute in the area of second language acquisition, it should examine how L2 pragmatic competence develops as L2 linguistic competence increases. Therefore, interlanguage pragmatics studies should be modelled on acquisitional pragmatics. As an effort to explore developmental features of pragmatic competence by linguistic proficiency, this study investigated the speech act behaviors of three linguistically distinctive groups. A total of 159 English learners, which consisted of high school 1st and 2nd graders, university freshmen, and university seniors, participated in this study. Their written responses to the 7 situations in the Discourse Completion Test (DCT) were analyzed in terms of response length, vocabulary, request forms, and the use of please. The three groups showed different behavioral patterns in the realization of requests and complaints, utilizing different linguistic strategies to be responsive to the social factors. For future research, expanding learner population to include very low and high level learners, developing a new research tool other than DCT, a more systematic grouping by linguistic proficiency were suggested.