In 163 consecutively irradiated patients with Hodgkin's disease, Stage I–III, herpes zoster subsequently occurred in 31 (19%). The incidence of zoster was increased in patients with mixed cellularity histology, Stage III disease, and in those patients with early stages treated with extensive irradiation. The majority of patients developed shingles within 6 months of primary treatment, a result suggestive of immunosuppression by lymphoma and/or irradiation, and was not associated with a high incidence of relapse. In those whose zoster occurred later than 6 months following primary therapy, a high incidence of lymphomatous recurrence (10/13) was noted, making herpes zoster an important prognosticator only in these selected individuals.