This paper critically reviews empirical studies of sex differences in preschool children's spontaneous speech at the levels of phonology, syntax/grammar, semantics, and conversational usage. A discussion of McCarthy's 1930 study includes consideration of methodological issues of data collection and analysis as well as the results of the study. It is suggested that further research include longitudinal study of the stability of early sex-typed vocalization/ verbalization patterns in infants and study of the relationship of sex role learning to sex-differentiated communicative behaviors. (30pp.)