A nationwide study of acute myocardial infarction in Israel was carried out over a one year period. There were 2,504 new and 968 repeated attacks. Annual incidence rate of first attacks was 0.9 per 1,000 (1.3 in men and 0.5 in women). Incidence was highest among the European born in both sexes. But, while the pattern of the native born men was similar to that of those born in Europe, it approached the incidence of the Asian African born in women. The sex ratio was relatively higher in those ethnic groups where male incidence was relatively higher and vice versa. Length of residence in the country had little effect on the incidence rates.