The development of children's imitative behavior is investigated in the natural environment. Data were obtained on 24 children over a nine month period during the second and third years of life. Sources of data consisted of descriptive accounts of imitation by mothers trained in observational recording. Although most of the incidents of imitation consisted of immediate repetitions of the behavior of models, incidents of delayed imitation increased from late infancy to early toddlerhood. Several developmental changes in the content of children's imitations also occurred during this period. The imitation of affective behaviors and of noninstrumental behaviors decreased as children grew older. Increases with age were found for caretaking, self-care, and household task behaviors, other-directed discipline and control behaviors, social interaction behaviors, and mannerisms and expressive characteristics of models. The overall pattern of findings suggest that imitation is an important process in the early acquisition of competent behavior patterns and that imitation of conventionally competent social and instrumental behavior patterns increases with age.