This experimental study has three aims: (1) to give a detailed description of imitative behavior as it develops during the first six months of life; (2) to compare imitative responses perceived through visual, kinesthetic and auditory modalities; and (3) to describe and explain the regulating mechanisms and processes present in the early development of imitation. To accomplish these aims, 12 first-born female infants were tested in their homes every two weeks between the ages of 1 and 6 months. A total of eight visual, three kinesthetic and three auditory tests were administered. Thirteen behavior categories were observed during both the control and reaction periods. The two hypotheses formulated to guide the research are supported by the data presented in the three main sets of results. These results show that: (1) imitation exists as early as 1 month of age but is limited to certain types of models; (2) these first imitative responses wane between 2 and 3 months of age; and (3) there is absence of imitative response during the first 2 months of life to some other types of models, (i.e. auditory) but once imitation to these models comes in, it increases with age. (SDH)