Two hundred ninety-five Greenlanders, 5% of the population of Greenland, aged 40 years or more, were investigated regarding primary osteoarthrosis of the knee. The pathological changes were categorized as mild, intermediate, or severe. Eighty-six (29%) of the patients were found to have osteoarthrosis and the mild form accounted for 72% of these, while only one individual was found to have severe osteoarthrosis. Significantly more individuals from the West coast of Greenland (a mixed Eskimo-European population) than individuals from the East coast (genuine Eskimos) were found to have osteoarthrosis of the knee (38% and 18%, respectively). An investigation of the sex distribution revealed more soteoarthrosi among West coast women than among East coast women (P less than 0.05), whereas no such differences were found among the men. It was speculated that the difference between the rates of osteoarthrosis of the knee in the two population groups might reflect differences in occupation and possibly also a genetic predisposition.