Two subsequent series of patients with Hodgkin's disease (HD) treated according to different therapeutic plans were compared: the study made it possible to analyze the role played by therapy in influencing the individual importance of a group of well-known prognostic factors. Study 1 concerned 667 patients treated in the period 1971-1979 without special measures for mediastinal bulky disease and with four-drug chemotherapy regimens (MOPP, COPP, ABVD) for stage B or IV. Study 2 included 220 patients treated between 1980 and 1984 with combined sandwich chemoradiotherapy when mediastinal bulk was present, and with eight-drug alternating chemotherapy regimens for stages B or IV (MOPP/ABVD, CcVPP/ABVD). Distribution of epidemiologic and clinical characteristics as well as staging accuracy were comparable in the two series. Only sex, serum albumin at onset and success or failure in achieving complete remission showed the same ability to discriminate survival in both studies. Age, stage and histology retained a reduced role in Study 2, where it was found they could be handled as binary variables, i.e. more or less than 50 years of age, stage IV or other stages, lymphocyte depletion histotype or other types. The influence of B symptoms on survival was sharply decreased in patients treated with alternating chemotherapy regimens, whereas combined sandwich therapy showed a truly leveling effect on the role of mediastinal bulk, which has to be considered a very unfavorable factor with other treatments. In HD the evaluation of clinical findings with respect to their impact on prognosis is crucial for validating and graduating the staging process, and for matching the intensity of the therapy to the needs of the patient. The ongoing evolution in the roles of single prognostic factors due to therapy needs periodic reevaluation for proper adjustments of therapeutic strategies.