Spontaneous full passives and related constructions from 234 children aged 2;0 to 13;11 and elicited passives from 262 college students were analyzed. Full passives were classified as reversible (The dog was chased by the girl), instrumental non-reversible (The lamp was broken by [or with] the ball), or agentive non-reversible (The lamp was broken by the girl). The agentive non-reversible did not appear until after age 9; and until age 11, no child produced both reversible and non-reversible passives. All the children used the passive in a semantically restricted way, but not in the same way. The possible developmental course of the full passive was traced for children who initially used only reversible passives versus those who initially used only instrumental non-reversible passives. From this study, the following conclusions can be drawn: (1) language acquisition is not complete by middle childhood; (2) individual differences exist in language learning "strategies"; children use analogy to learn grammatical rules; (3) the relationship between comprehension and production is complex; and (4) the distinction between semantics and syntax is often arbitrary. (Author/AM)