Individual-level social capital was assessed for prediction of mortality in a nationally representative study population aged 30-99 years at the baseline. A total of 90% of the original sample had participated in a comprehensive health examination (Mini-Finland Health Survey) in 1978-1980. After the first 5 years of the 24-year follow-up period, 1,196 of 3,014 men and 1,280 of 3,689 women died. Individual-level social capital was determined by factor analysis that revealed three factors: residential stability, leisure participation and interpersonal trust. Factor analysis showed a gender difference in leisure social participation. All-cause mortality and cardiovascular mortality were analyzed using Cox proportional hazard models. Adjusted for demographic, life style and biological risk factors, and for health and socio-economic status, leisure participation was associated with reduced all-cause mortality in men (hazard ratio, HR: 0.94; 95% confidence interval, CI: 0.89-1.00). This association seems to be related to economic status in men. Age modifies the effect of interpersonal trust on all-cause mortality in men. In women, leisure participation (HR: 0.96; 95% CI: 0.91-1.00) and interpersonal trust (HR: 0.69; 95% CI: 0.51-0.93) predicted all-cause mortality, and the latter also cardiovascular mortality (HR: 0.93; 95% CI: 0.86-1.00). The associations between individual-level social capital and mortality are gender- and age-related. Understanding the gender and age perspectives appears to be essential for better insight into the interrelations between social capital and health.