The objectives of the study were to compare different aspects of social support between caregiving partners of men with AIDS and partners of healthy men and to examine the association of social support with positive and negative mood. Data were collected in a longitudinal study of 244 gay male caregivers and 61 comparison gay male noncaregivers. Measures included perceived positive support; social conflict; sought support; amount, types, and sources of received support; relationships with family; and positive and negative mood. Cross-sectional analyses and changes between baseline and 2 years were examined. No significant differences were found between the caregivers and noncaregivers in most aspects of social support. Regression analyses showed (a) caregiver status was associated with positive and negative mood (caregivers reported lower positive mood and higher negative mood) at baseline, but not at 2 years; (b) perceived support was the only variable significantly associated with positive mood at baseline and at 2 years; and (c) social conflict (at both times) and perceived support, amount of received support, and having a family confidant (at one of the time periods) were associated with negative mood. The findings support the importance of distinguishing between perceptual and behavioral aspects of social support and their relation to both positive and negative mood.