This article describes the test-retest reliability of a scale comprising five dimensions of social support: material, emotional, informational, affective, and positive social interaction. In the study, a sample of 192 employees at a university in Rio de Janeiro filled out the same questionnaire on two occasions, 15 days apart. Measures of stability used were the intraclass correlation coefficient (ICC), weighted kappa statistic, and log-linear models. Internal consistency was evaluated using the Cronbach's alpha coefficient. Social support dimensions showed internal consistency ranging from 0.75 to 0.91 at test, and 0.86 to 0.93 at retest. The ICC ranged from 0.78 to 0.87 in the five dimensions of the scale, with no substantial differences by gender, age, or level of schooling. For most questions, the "agreement plus linear by linear association" and "quasi-association" log-linear models gave the best fit. According to these results, the reliability of the instrument was considered adequate, enabling it to be used in ongoing assessment of associations between social support and health-related outcomes in a cohort study (the Pro-Health Study) recently begun in Rio de Janeiro.