The research reported is part of an investigation into the acquisition of grammar, using nonlinguistic information from situational and behavioral context to analyze the development of linguistic expression. Three children were seen for approximately 8 hours, every 6 weeks, in their homes, from the age of 19 months--soon after the earliest occurrence of two-word constructions. Each sample of spoken language was obtained during (1) play with a selected group of toys, (2) eating, dressing, and toileting, and (3) play with a peer. The language of one of the children was described in terms of 'pivot grammar' with linear relationship between constituents and specification of a small class of forms which occurred in pivotal constructions with a large class of lexical constituents. In contrast, the grammars of the other children exhibited an hierarchical structure with constituents derived from more than one node in a phrase-marker representation. For all three children, negation appeared as one of the first syntactic structures with identifiable semantic function; negative sentences could be classified as signalling nonexistence, rejection, or denial. (Author/LK)