Over the period 1972-1985, 2729 cases of Hodgkin's disease were diagnosed in Los Angeles County, and 2492 were subclassified using the Rye classification. The occurrence of these cases was examined in relation to age, sex, race, place of birth, social class, occupation, and year of diagnosis. The pattern of nodular sclerosis occurrence conformed to expectations, supporting the polio model of etiology for this subtype. However, the risk pattern of mixed cell disease was quite distinct from that of nodular sclerosis, suggesting that the two may not share a common etiology. The pattern of lymphocyte predominance in Hodgkin's disease, with a special prominence in younger blacks, resembled neither that of nodular sclerosis nor that of mixed cell disease. The cases of lymphocyte-depletion Hodgkin's disease showed no distinctive epidemiological features, and its continued classification with nodular sclerosis and/or mixed cellularity can be justified solely by histological or biological evidence.