Does spreading activation from incidentally encountered hints cause incubation effects? We used Remote Associates Test (RAT) problems to examine effects of incidental clues on impasse resolution. When solution words were seen incidentally 3-sec before initially unsolved problems were retested, more problems were resolved (Experiment 1). When strong semantic associates of solutions were used as incidental clues, however, it did not improve resolution (Experiments 2 and 4). The semantic associates we used as incidental clues primed our RAT solution words in a lexical decision task, but they did not facilitate impasse resolution unless participants were explicitly instructed to use the associates as hints to the retested problems (Experiment 4). The results do not support the theory that spreading activation is a sufficient cause of incubation effects, and suggest that serendipitously encountered clues (i.e., words that are semantically related to RAT solutions) have no automatic benefit on impasse resolution in RAT problem solving.