Outcomes and perceived intentions influence how individuals reciprocate others' actions. Using an experiment to disentangle the impact of outcomes and intentions, this paper provides first evidence about the relative importance and interaction of these two determinants of reciprocal behavior. In our data, outcomes strongly dominate intentions in their impact on reciprocal behavior. Furthermore, intentions and outcomes are complementary and, hence, interact in inducing reciprocity: the impact of a good outcome on reciprocal behavior is magnified by kind intentions and vice versa. To uncover the drivers of outcome and intention effects, we elicit social norms from third parties and provide evidence of their significant yet limited explanatory power: comparing a social-preference-based explanation to the social-norm-based explanation reveals that the former explains actual choices much better than the latter.