Prostate cancer is one of the most frequent tumours in males. Globally about 235,000 new cases were estimated to occur in 1980. The cancer is particularly frequent in North America, where rates in blacks are often double those in whites, and in several European countries, being rare in much of Asia. After migration to the US, Chinese and Japanese show substantial increases. Incidence may be distorted by inclusion of varying numbers of so-called 'latent' cancers; for some comparisons mortality data are preferable. 'Small' latent cancers seem to be uniformly distributed irrespective of the incidence of the clinically manifest form. The incidence of prostate cancer seems to be increasing in most populations, particularly in Asia and Eastern Europe. In general, mortality follows suit. Birth cohort analysis shows that for US non-whites, cohorts born before 1896-1900 showed an increase in mortality for all age groups, but the death rates fell for cohorts born subsequently, a phenomenon also observed in Australia and England and Wales.