This longitudinal study investigates the impact of social participation, trust and the combinations of social participation and trust on the incidence of first time acute myocardial infarction (AMI) in the population of Scania, southern Sweden. It is based on the cross-sectional 2000 public-health survey in Scania with a 59% participation rate and 13,604 participants, and prospective morbidity/mortality data collected for three years (January 2000-December 2002). The study cohort was followed prospectively to examine first ever AMI. Hazard rate ratios (HRR) for first time AMI in the social participation, trust and social participation/trust combinations were calculated in a Cox regression model with adjustments for age, sex, education, economic stress, daily smoking, leisure time physical activity, body mass index (BMI), and self-reported health. The prevalence of low social participation was 32.8% among men and 31.5% among women. The prevalence of low trust was 40.0% among men and 44.2% among women. The three-year first time AMI rate was significantly higher among people with higher age, low education, daily smoking, poor self-reported health (among men), low social participation, and the combinations of low social participation/high trust and low social participation/low trust. The results show that low social participation but not trust was significantly associated with first time AMI after adjustment for age and sex. The positive association between low social participation and myocardial infarction remained significant after further adjustments for education, economic stress, daily smoking, physical activity and BMI, and became not significant only after additional adjustment for self-reported health, HRR 1.3 (0.9-2.0). High trust in combination with low social participation as well as low social capital (low trust/low social participation) were significantly associated with AMI, but after multiple adjustments only the low social participation/high trust category remained significant, HRR 1.6 (1.0-2.6).