A retrospective study was undertaken at the Institut Gustave Roussy (IGR) to determine the predictive ability of changes in the erythrocyte sedimentation rate (ESR) during posttherapy periods for early relapse (within 18 months from start of therapy) and long-term survival in Hodgkin's disease (HD). Three hundred one patients with clinical stages (CS) I or II HD entered in the European Organization for Research and Treatment of Cancer (EORTC) clinical trials were included in this study. All relevant data and long-term follow-up were available for these patients. A stepwise logistic regression was performed to assess the prognostic value of ESR changes independent of other prognostic parameters and treatment. The incidence of early relapse was found to be significantly increased in patients in whom ESR remained elevated (greater than 30 mm at one hour) after completion of therapy, regardless of the value before therapy. This was true whether the ESR was elevated in plateau fashion, oscillating between normal and abnormal, or was lower than at onset, but still abnormal. Moreover, early relapse predicted by elevated ESR posttherapy was associated with poor survival despite subsequent initiation of combination chemotherapy. Thus, the persistence of an abnormal ESR appears to be a reliable indicator for high probability of early relapse and subsequent poor prognosis. This might be introduced as a prognostic variable in the design of future therapy programs for HD.