There has long been speculation that socially-involved individuals suffer less illness, overcome sickness more readily, and experience better health outcomes than more socially isolated persons. This study describes social network characteristics, and determines whether social network affects health outcomes in the geriatric population. Data from 1270 consecutive patients seen in the outpatient Geriatric Assessment Clinic (GAC) of the University of Nebraska Medical Center between August 1988 and May 1999 were analyzed. Social network was measured by the Social Network Index (SNI). Younger age, higher income and higher education were related to a broader social network. A larger social network was generally associated with lower caregiver burden, higher functional status and better cognition. Men with the smallest social networks were found to be at significantly higher risk of death than women with larger social networks (HR 4). After adjusting for age (HR 1.04, CI 1.03-1.06), income (HR 1.00, CI 1-1), education (HR, NS), IADL (HR 0.97, CI 0.95-0.99), CIRS (HR 1.08, CI 1.05-1.10) and informal service use (HR, NS), the risk of death for subjects based on SNI is only significant in the comparison between SNI III and SNI I (HR 0.67, CI 0.50-0.91). SNI I males are at significantly increased risk of death compared with all other groups. The average number of years from initial visit to death for SNI I males is only 2.8 years. These results are consistent with the literature, which suggests men are more affected by social isolation and have decreased survival compared with females. The influence of SNI on mortality in this frail, elderly group appears to be diluted by the presence of functional disability and a high degree of comorbid illness.