The evidence of construct validity that resulted from conjoint testing of two measures of social support, the Personal Resource Questionnaire (PRQ85) and the Cost and Reciprocity Index (CRI) is presented. Both instruments were used with two samples of adults, 333 who were part of a large health project and 99 who participated in a methodological study. The PRQ85 and CRI appear to tap the construct of support yet are not highly redundant. Both tools demonstrated similar curves of relationships to external criteria. Dissimilar patterns of relationships with negative mood states indicated an area of need for future study.