In Italy three areas have been enrolled in the MONICA Project, two being located in Northern Italy (Area Brianza and Area Friuli) and one in Central Italy (Area Latina). This report concerns the comparison of the first year mortality and registration data of two areas, Area Latina (1983) and Area Brianza (1985), for men and women aged 25-64. In Area Latina, the age-standardized mortality rates for all causes, for all coronary heart disease, and for stroke are respectively 483, 83 and 42 per 100,000 for males, and 252, 14 and 32 per 100,000 for females. In Area Brianza, the age-standardized mortality rates for all causes, for all coronary heart disease, and for stroke are respectively 541, 94 and 38 per 100,000 for males, and 249, 19 and 24 per 100,000 for females. For males the attack rate for coronary events is similar in Area Latina and Area Brianza but the distribution of events in the several diagnostic categories is different. For females the coronary attack rate is higher in Area Latina than in Area Brianza. The implications of these data are discussed mainly from the methodological point of view.