This report describes part of a longer study on sentence comprehension. The long range goal is to identify distinct levels of processing in terms of the types of linguistic and extralinguistic information each level uses. The focus of this part of the study is sentences with filler-gap relations, such as, "This is the girl the teacher wanted to talk to" and "This is the girl the teacher wanted to talk." Forty-eight sentences were constructed modelled on these two examples. The sentences, intermingled with other sentences of varying structures, were presented on a computer-controlled video display to 48 college-student subjects who were instructed to indicate whether or not they thought they understood each sentence, on the basis of an intuitive decision. Another experiment was conducted with sentences in which the verbs prevented possible ambiguity, in order to determine whether or not other information is used in initial comprehension. It was found that readers initially fill a gap in a sentence with the most salient possible filler, and that this strategy is followed even when semantic control information about a verb seems to prohibit it. (AMH)