Previous research on the effects of mastery beliefs on appraisal of stress usually employed generalized measures such as locus of control and produced mixed findings, depending, in part, on whether the encounters experienced were within the domains of control assessed. The present study examined the effects of situation-specific mastery and satisfaction with social support on the appraisal of a situation's stressfulness by 147 male college students. Mastery was positively correlated with the appraisal of desirability of the situation and accounted for 36.9% of the variance. Greater satisfaction with social support was related to more positive appraisals by subjects with high mastery but with more negative appraisals by subjects with low mastery. Mastery and satisfaction with support also interacted to moderate the effects of the number of stressors experienced on total stress. For subjects who faced many stressors, those with low mastery experienced high stress regardless of their satisfaction with support, whereas those with high mastery experienced high stress if their satisfaction with support was low, but moderately low stress if satisfaction with support was high.