BACKGROUND: We studied the age and gender difference between acute coronary heart disease and ischaemic stroke risk and examined the extent to which such a difference may be explained by known risk factors. METHODS: Data from Finnish and Swedish population-based cohorts including 9278 individuals were collaboratively analysed. Hazards ratios (95% confidence intervals) for coronary heart disease and stroke incidence were estimated using the Cox-proportional hazards model. RESULTS: The incidence of coronary heart disease and stroke was higher in all age groups in men than in women, and the gender difference was more marked for coronary heart disease than for ischaemic stroke. There was a 10-year lag in the development of coronary heart disease and stroke in women compared with men. The multivariable adjusted hazard ratios for the incidence of coronary heart disease in men and women were 3.87 (2.49-6.02) and 1.71 (1.07-2.74) at age 50-59 years, and 7.22 (4.59-11.36) and 3.49 (2.18-5.57) at age 60-69 years compared with women aged 40-49 years. For ischaemic stroke, they were 2.64 (1.45-4.82) and 2.17 (1.18-3.97) at age 50-59 years, and 5.19 (2.81-9.58) and 4.89 (2.67-8.97) at age 60-69 years, respectively. CONCLUSIONS: Acute coronary heart disease and ischaemic stroke events appeared approximately 10 years earlier in men than in women, and these rates remained higher in men than in women in all age groups. The gender difference was more marked for coronary heart disease than for ischaemic stroke. This may be taken into account when developing interventions and treatment strategies.