Although disfluencies such as uh are generally not treated as linguistic items, our results suggest that they can affect syntactic parsing. Using a grammaticality judgment task, we demonstrate that disfluencies are able to affect the syntactic parse of a sentence in two ways. First, disfluencies can make syntactic reanalysis more difficult by coming between an ambiguous constituent and a disambiguating item. Second, the pattern of disfluencies in spontaneous speech may be used by the listener to guide the parse of a sentence. Thus, although disfluencies have often been viewed as pragmatic phenomena, they can affect the language comprehension by influencing its parsing procedures.