Are people who are funny more attractive? Or does being attractive lead people to be seen as funnier? The answer may depend on the underlying evolutionary function of humor. While humor has been proposed to signal "good genes," the authors propose that humor also functions to indicate interest in social relationships-in initiating new relationships and in monitoring existing ones. Consistent with this interest indicator model, across three studies both sexes were more likely to initiate humor and to respond more positively and consider the other person to be funny when initially attracted to that person. The findings support that humor dynamics--and not just humor displays--influence romantic chemistry for both men and women, suggesting that humor can ultimately function as a strategy to initiate and monitor social relationships.