Research on insight-the phenomenon of suddenly solving an apparently intransigent problem--has been hampered because stimulus problems have been few, ad hoc, heterogeneous, and difficult to solve. Responding to the need for a larger pool of problems of a similar type and of varying level of difficulty, we report an experiment testing the validity of rebuses as insight problems. A rebus combines verbal and visual clues to a common phrase, such as PAINS ("growing pains"). Solving a rebus requires breaking implicit assumptions of normal reading, similar to the restructuring required in insight. We hypothesized that, the more implicit assumptions are involved, the more difficult the solution. The results of a two-part experiment supported the hypothesis, with participants solving more problems involving one assumption than they did problems involving two or more. Also, rebus performance correlated significantly with self-rated insight and with scores on remote associates, but not with general verbal ability. The findings suggest that rebus puzzles may be a useful source of theoretically grounded insight problems.