Comparison of stroke incidence in various parts of the world is difficult because differences in diagnostic criteria, medical facilities and age-sex distributions are often not taken into account. We calculated age-sex standardized incidence ratios (SIR) of stroke in 37 regions based on recent reports. The USA (1976) was taken as the standard population. In western countries SIRs varied from 0.8 to 2.1. In China and Japan, SIRs varied from 0.7 to 3.6. While the lowest and highest SIRs differed by a factor of 5, only 6 of the 37 studies yielded a SIR of more than 2.0 or below 0.75. Of these, 4 were from China and Japan. The highest ratios were based on a very intensive door-to-door survey and probably should not be compared to less intensive studies. We conclude that world-wide variation in age-sex adjusted stroke rates is relatively small.