The first-degree relatives (parents, siblings and children) of 284 patients complaining of discogenic low-back pain (Group I), 114 patients who had undergone surgery for lumbar disc herniation (Group II), and 280 individuals who had never complained of low-back pain (Group III) were surveyed by self-completed questionnaires. Of the families in Group I and Group II, 35 and 37%, respectively, had at least one member with a history of discogenic back pain and 5 and 10%, respectively, had one or two members who had undergone disc surgery. Of the asymptomatic subjects in Group III, only 12% had at least one or more affected relatives and 1% had a relative who had undergone disc surgery; of the affected families, 41% had two or more members with a history of back pain. The proportion of symptomatic relatives in the affected families was higher among sedentary workers and motor vehicle drivers than among heavy or light manual workers. An immunogenetic study comparing the frequencies of HLA-A, B, and C antigens in 39 patients who had undergone lumbar disc surgery with those in 60 asymptomatic individuals showed no significant differences between the two groups. This study indicates that there is a strong familial predisposition to discogenic low-back pain, and suggests that the etiology of degenerative disc disease is related to both genetic factors, not linked to the HLA antigen system, and environmental factors.