In a multicentre study conducted by the Paul Ehrlich Society we tested 3482 Staphylococcus aureus strains, isolated in different hospitals in West Germany, Austria and Switzerland, against 12 antibiotics with standardized techniques between 1976 and 1982. In order to avoid mistakes in the classification of the strains into sensitive, intermediate and resistant, we adapted breakpoints to the population distribution. There were no marked changes in the incidence of sensitive strains during the period. Striking differences from one hospital to another were observed. The percentage of strains sensitive to penicillin remains low (27%). The other antibiotics studied show activity against 80-100% of strains.