Previous theories and research show clear divergences on the roles of the behavioral activation system (BAS) and the behavioral inhibition system (BIS) in depression. Across four studies, we examined the effects of a sad mood on the motivational pattern of sensitivity to reward and punishment. Psychological variables associated with such changes and implications for vulnerability to depression were also explored. For this purpose, we designed a state version of the extensively used BIS/BAS Scales (Carver & White, 1994). Using samples of undergraduate students, we found that both a natural (Study 1) and a laboratory-induced sad mood (Studies 2 and 3) generated a marked decrease in sensitivity to reward but did not alter sensitivity to punishment. Study 3a showed that participants' anxious attachment predicted larger decreases in sensitivity to reward after a sad mood induction. Study 3b extended these results by showing that sensitivity to reward, when assessed after the negative mood induction, predicted increases in dysphoria 7weeks later. Implications of the results for research on vulnerability to depression are discussed.