This study investigates the coordination of matrix and subordinate clauses within finite complement-clause constructions. The data come from diary and audio recordings which include the utterances produced by an American English-speaking child, L, between the ages 1;08 and 3;05. We extracted all the finite complement-clause constructions that L produced and compared the grammatical acceptability of these utterances with that of the simple sentences of the same length produced within the same two weeks and with that of the simple sentences containing the same verb produced within the same month. The results show that L is more likely to make syntactic errors in finite complement-clause constructions than she does in her simple sentences of the same length or with the same verb. This suggests that the errors are more likely to arise from the syntactic and semantic coordination of the two clauses rather than limitations in performance or lexical knowledge.