This paper investigates how people resolve syntactic category ambiguities when comprehending sentences. It is proposed that people combine: (a) context-dependent syntactic expectations (top-down statistical information) and (b) context-independent lexical-category frequencies of words (bottom-up statistical information) in order to resolve ambiguities in the lexical categories of words. Three self-paced reading experiments were conducted involving the ambiguous word ''that'' in different syntactic environments in order to test these and other hypotheses. The data support the top-down/bottom-up approach in which the relative frequencies of lexical entries for a word are tabulated independent of context. Data from other experiments from the literature are discussed with respect to the model proposed here.