Past research has shown rather consistently that positive mood states lead to increased helpfulness. In an expanded analysis of the published literature, we examined six distinct views about this relation: the focus of attention, objective self-awareness, separate process, social outlook, mood maintenance, and concomitance hypotheses. For each of 61 positive affect conditions in which it was possible to generate an effect-size estimate corresponding to the relative degree of helpfulness exhibited by positive mood subjects (compared with neutral affect subjects), judges assessed the contextual levels of variables relevant to each of the six hypotheses by reading the Method section of each article. Higher-order partial correlation coefficients were then calculated to isolate the independent contribution of each of the theoretically relevant variables to the variation among the 61 effect sizes. The results support the focus of attention, separate process, social outlook, and mood maintenance hypotheses, and partially support the objective self-awareness and concomitance hypotheses.