Two experiments examined the process of acquisition of sentence structure in the passive voice among young children. The subjects were several hundred monolingual French-speaking children aged 4-11 in schools in Liege, Belgium. The two experiments used different subject groups. In the first experiment, the children were required to interpret sentences of varying types (plausible and plausibly reversible, implausible but plausibly reversible, and plausible but not plausibly reversible active and passive sentences) presented in either a realistic or a fictitious instructional context. Results showed complex patterns of responses illustrating the influences of semantic and syntactic factors in sentence comprehension, and their evolution over time. In the second experiment, the subjects interpreted syntactically regular and anomalous passive sentences according to semantic type. Results suggest that when the formal syntactic marks of passivity play a major role in sentence interpretation, the influence of the agentive preposition is more important than that of the auxiliary and/or past participle. A view of the development of passive sentence comprehension that sees it as an evolutionary product of a flexible set of interpretive strategies relating semantic and syntactic factors is proposed. (Author/MSE)