The test performance of 120 Anglo, black, and Chicano third- and fifth-grade children is used to demonstrate the similarities between the processes of diachronic and ontogenetic language change. The instrument used measured the range of knowledge of several grammatical structures. Analysis and interpretation of results suggested the gradual emergence of grammatical control both within and among the categories studied. The children gained control of the following, in order of emergence: possessives, present tense, past tense, negation, comparative adjectives; sentence-combining transformations, and tag questions. The older, native speakers of standard English exhibited the highest degree of grammatical control. Chicano children, who learn English as a second language, exhibited the same order of emergence of control of grammatical structures as the native speakers. Sex was unimportant as a variable during the maturation phases but became more important during the adaptation phase. (Author/AA)