The perceptual complexity of sentences was assessed using a rapid visual presentation procedure. One-clause sentences with complement verbs were shown to be significantly harder to process than one-clause sentences with simple verbs. This result indicates the importance of the matrix verb in determining how S perceives sentence structure. It was also shown that, although there were differences within two-clause complement constructions, they were no harder to process than both kinds of one-clause sentence. This suggests that the presence of more than one underlying structure sentence does not always increase perceptual complexity.