To investigate if participation in sports increases the risk of developing osteoarthrosis of the hip, we did a case-control study on the sports activities of 233 men (up to age 49) who were recent recipients of a prosthesis because of severe idiopathic osteoarthrosis of the hip and 302 men randomly selected from the general population. Assessments of sports, job history, and health status were made by an interview. Men with high exposure to sports of all kinds combined (in hours) had a relative risk to develop osteoarthrosis of the hip of 4.5 compared to those with low exposure. Track and field sports and racket sports seemed to be the most hazardous to the hip joint. Men who had been exposed to high physical loads both from their occupation and sports had a relative risk of 8.5 to develop osteoarthrosis of the hip compared to those with low physical load in both activities. Potential confounding factors, such as age, body mass index, and smoking, were considered. Long-term exposure to sports among men seems to be a risk factor for developing severe osteoarthrosis of the hip; this is increased when combined with heavy load from occupation.