All accounts of language acquisition agree that, by around age 4, children's knowledge of grammatical constructions is abstract, rather than tied solely to individual lexical items. The aim of the present research was to investigate, focusing on the passive, whether children's and adults' performance is additionally semantically constrained, varying according to the distance between the semantics of the verb and those of the construction. In a forced-choice pointing study (Experiment 1), both 4- to 6-year olds (N = 60) and adults (N = 60) showed support for the prediction of this "semantic construction prototype" account of an interaction such that the observed disadvantage for passives as compared to actives (i.e., fewer correct points/longer reaction time) was greater for "experiencer-theme" verbs than for "agent-patient" and "theme-experiencer" verbs (e.g., "Bob was seen/hit/frightened by Wendy"). Similarly, in a production/priming study (Experiment 2), both 4- to 6-year olds (N = 60) and adults (N = 60) produced fewer passives for "experiencer-theme" verbs than for "agent-patient/theme-experiencer" verbs. We conclude that these findings are difficult to explain under accounts based on the notion of A(rgument) movement or of a monostratal, semantics-free, level of syntax, and instead necessitate some form of semantic construction prototype account.