The family histories of 131 patients with histologically defined Hodgkin's disease (HD) were studied and 2,517 first and second degree relatives and spouses were identified and followed-up. The causes of death in deceased relatives were ascertained from death certificates. The numbers of deaths from selected causes were compared with the numbers that would be expected if the relatives had suffered the same mortality rates as the Scottish national population. A 4-fold increase in deaths due to HD was found among first and second degree relatives of patients with the disease (6 cases observed compared with 1.4 expected). Five of the 6 familial cases were related to index patients with the mixed cellularity form of the disease, the remaining case was the brother of a patient with the lymphocyte-depleted form of the disease. The increased risk was seen among relatives of both young and older patients and there was no consistent intrafamilial similarity in age of onset or time of onset of disease.