The nodular form of lymphocyte predominance Hodgkin's disease has been shown to be immunophenotypically distinct from the histologically diffuse form and from other types of Hodgkin's disease. We undertook a clinicopathological study of 73 cases to determine whether any clinical differences between the nodular and diffuse subtypes could be discerned. Patients with the diffuse form (n = 41) tended to have a course similar to that of other types of Hodgkin's disease; there were few relapses and only two deaths due to Hodgkin's disease. In contrast, patients with the nodular form (n = 32) had significantly more relapses, which were independent of stage or treatment and equally distributed up to 10 years after initial therapy. Despite the frequent relapses, patients with the nodular form had an indolent course, and there was only one death due to Hodgkin's disease. There were seven fatal second cancers and two non-neoplastic treatment-related deaths, equally distributed between the nodular and diffuse groups. We conclude that nodular lymphocyte predominance Hodgkin's disease may have important clinical as well as immunophenotypic differences from other forms of Hodgkin's disease, and that patients with this condition should be followed carefully because of the possibility of late relapse.