The intent of this study was to examine the development of three aspects of preschoolers' private speech: coefficients of egocentricism, the extent to which speech regulates actions, and the syntactic and semantic structures of individual utterances. Forty-one randomly chosen preschoolers (26 females, 15 males) were placed in three age groups (3, 4, or 5 years). Children were videotaped while they did two age-appropriate puzzles. Three-year-olds' coefficients of egocentricism were significantly greater than coefficients for both 4- and 5-year-olds. Regardless of age, children talked while acting. Three-year-olds asked most questions-to-self. All children's utterances were syntactically complex. Semantic structure analyses indicated that regardless of age, children encoded patient case utterances, perceptually present objects, and state verbs. All children tended to use private speech to encode names of puzzle pieces and locations for pieces while they were acting. (Author/MP)