In a prospective study, sixty-five histologically verified Swedish cases of Hodgkin's disease were HL-A typed. The antigen frequencies in the patient group did not deviate from a group of normal controls. The frequency of HL-A8 was slightly increased in patients over 40 years (P less than 0.05). HL-A12 was markedly increased in patients below 40 years with a favourable histopathology (P less than 0.001). No association between sex or clinical stage and distribution of HL-A phenotypes was observed. The number of T-lymphocytes in blood and the spontaneous DNA synthesis and DNA synthesis induced by concanavalin A, pokeweed mitogen, phytohemagglutinin and PPD antigen in blood lymphocytes in vitro were determined in 60 patients. A significant increase of HL-A28 was noted in patients with advanced disease (P less than 0.01) and in patients responding poorly to PPD (P less than 0.001) and PWM (P less than 0.01). No correlation between HL-A antigen distribution and T-lymphocyte counts was observed.