An eye-movement study examined the processing of expressions requiring complement coercion (J. Pustejovsky, 1995), in which a noun phrase that does not denote an event (e.g., the book) appears as the complement of an event-selecting verb (e.g., began the book). Previous studies demonstrated that these expressions are more costly to process than are control expressions that can be processed with basic compositional operations (L. Pylkkanen & B. McElree, 2006). Complement coercion is thought to be costly because comprehenders need to construct an event sense of the complement to satisfy the semantic restrictions of the verb (e.g., began writing the book). The reported experiment tests the alternative hypotheses that the cost arises from the need to select 1 interpretation from several or from competition between alternative interpretations. Expressions with weakly constrained interpretations (no dominant interpretation and several alternative interpretations) were not more costly to process than expressions with a strongly constrained interpretation (1 dominant interpretation and few alternative interpretations). These results are consistent with the hypothesis that the cost reflects the on-line construction of an event sense for the complement.