The statistical significance of familial lymphoma in first-degree blood relatives was evaluated for the series of all lymphoma cases referred to our department since 1968. Four pairs of immediate relatives with Hodgkin's disease (HD) were found among 183 patients diagnosed between 1960 and 1980. The expected number during that period was 0.45. Thus, close relatives of HD patients had about ninefold increased risk of the disease (P less than 0.005). Mixed-cellularity was the most common subtype in these familial cases (6/8 patients). There were three pairs of close relatives with non-Hodgkin's lymphoma (NHL) among 532 patients diagnosed during the same period, 1960-1980. The expected number was 3.86. These findings further indicate that HD may differ from NHL with regard to familial clustering.