A register-based cohort study was performed to investigate if men and women in certain occupations with high physical workload had increased risks of developing severe symptomatic osteoarthrosis of the hip and knee, resulting in hospital care. The study population consisted of 250,217 people from the 1980 census, in blue-collar occupations, who had reported the same occupation in the 1960 and 1970 censuses. The study population was followed for hospital care for osteoarthrosis of the hip and knee during 1981-1983 by linkage to the Swedish Hospital Discharge Register. Different blue-collar occupations were classified as high or low with regard to exposure to forces acting on the hip and knee and the frequencies of the outcomes were compared. Male farmers, construction workers, firefighters and some food processing workers had an excess risk of hospitalization due to osteoarthrosis of the hip. Male farmers, construction workers and firefighters also had increased risks of osteoarthrosis of the knee. Female mail carriers had an excess risk of osteoarthrosis of the hip, and female cleaners, of osteoarthrosis of the knee. The findings support the hypothesis that heavy physical work load contributes to osteoarthrosis of the hip and knee.