The purpose of this study was to explore whether 13 children with specific language impairment (SLI; ages 5;1-8;0 [years;months]) were as proficient as typically developing age- and vocabulary-matched children in the production of finite and nonfinite complement clauses. Preschool children with SLI have marked difficulties with verb-related morphology. However, very little is known about these children's language abilities beyond the preschool years. In Experiment 1, simple finite and nonfinite complement clauses (e.g., "The count decided that Ernie should eat the cookies"; "Cookie Monster decided to eat the cookies") were elicited from the children through puppet show enactments. In Experiment 2, finite and nonfinite complement clauses that required an additional argument (e.g., "Ernie told Elmo that Oscar picked up the box"; "Ernie told Elmo to pick up the box") were elicited from the children. All 3 groups of children were more accurate in their use of nonfinite complement clauses than finite complement clauses, but the children with SLI were less proficient than both comparison groups. The SLI group was more likely than the typically developing groups to omit finiteness markers, the nonfinite particle "to", arguments in finite complement clauses, and the optional complementizer "that". Utterance-length restrictions were ruled out as a factor in the observed differences. The authors conclude that current theories of SLI need to be extended or altered to account for these results. (Contains 6 tables and 2 figures.)