This article describes the second phase of testing the Norbeck Social Support Questionnaire (NSSQ), an instrument designed to measure multiple dimensions of social support. Three studies were conducted to provide a normative data base and to further test validity. In the first study, data from 136 employed adults were obtained. The amount and type of support available for a functioning group of male and female respondents and sources of support for this sample are described. In the second and third studies, the instrument was found to be very stable over a seven-month interval and sensitive to changes within the social support networks of a group of graduate students during their first year of study. Construct validity of the instrument was established by comparing convergent and discriminant constructs to the NSSQ. Concurrent validity with another social support questionnaire was demonstrated. Predictive validity was tested in a sample of 53 graduate students through assessing the buffering effect of social support on measures of negative mood following life stress. Two NSSQ subscales, aid and duration of relationships, had significant interaction effects with life stress on the outcome of negative mood. Duration of relationships also had a significant main effect. After subtracting the main effect for life stress from the overall R2 in the multiple regression analysis, the NSSQ functional support subscales and their interactions with life stress accounted for 19 percent of the variance on negative mood, and the NSSQ network property subscales and their interactions accounted for 20 percent of the variance.