Preliminary reports suggested a prognostic significance for serum levels of soluble CD30 (sCD30) in patients with Hodgkin's disease (HD). In this study, we investigated the prognostic impact of sCD30 concentration at diagnosis in relation to the other recognized prognostic parameters in 303 patients with HD observed in three different institutions between 1984 and 1996. sCD30 levels were correlated with stage, presence of B symptoms, and tumor burden. High sCD30 levels entailed a higher risk of poor outcome, and the event-free survival (EFS) probability at 5 years for patients with sCD30 levels >/=100 and less than 100 U/mL was 59.9% (95% confidence interval [CI], 40.6% to 65.9%) and 87.5% (95% CI, 81.5% to 91.6%), respectively (P < .001). On the basis of the results of univariate analysis of 14 pretreatment characteristics, we included five prognostic factors (high sCD30 serum level, stage III-IV, B symptoms, low hemoglobin level, and age >/=50 years) into a multivariate model. High sCD30 and advanced stage were independently associated with an unfavorable prognosis. Their combined evaluation identified patients at high risk (stages III and IV and sCD30 >/=100 U/mL: EFS, 46.9%) and low risk (stages I and II with sCD30 <100 U/mL: EFS, 88. 7%) of treatment failure (P < .001). We conclude that the combined evaluation of sCD30 serum level and stage at presentation identifies patients with HD at high risk of an unfavorable outcome.