Caregivers of Alzheimer's disease patients often suffer from depression. Using a longitudinal treatment/control study, we examined the effects of a comprehensive support program on depression in spouse-caregivers. This psychosocial intervention program treats the primary caregiver and family members over the entire course of the disease through individual and family counseling, the continuous availability of ad hoc counseling, and support group participation. In the first year after intake, the control group became increasingly more depressed, whereas the treatment group remained stable. By the eighth month, treated caregivers were significantly less depressed than those in the control group. These results suggest that enhancing long-term social support can have a significant impact on depression in caregivers.