CD20 can be expressed in Hodgkin and Reed-Sternberg (HRS) cells of classical Hodgkin's disease (HD), but its clinical significance remains controversial. Therefore, we correlated CD20 expression with presenting features and clinical outcome of untreated patients with classical HD. Patients were eligible if they were previously untreated and human immunodeficiency virus-1 negative, had biopsy-proven classical HD, and if pretreatment paraffin-embedded tumor tissue was available. CD20 expression was determined by immunohistochemistry without knowledge of clinical outcome. A tumor was considered positive if any HRS cells expressed CD20, but other cutoffs for number of CD20-positive HRS were also investigated. We identified 598 patients whose median age was 30 years and of whom 55% were male. HRS cells expressed CD20 in 132 (22%) of 598 patients with classical HD. When any percentage of CD20 expression in HRS cells was used as a cutoff, the 5-year failure-free survival (FFS) for positive versus negative tumors was 86% versus 84%, respectively, for 302 patients treated with doxorubicin, bleomycin, vinblastine, and dacarbazine or equivalent regimens (P =.7 by log-rank test), 74% versus 77%, respectively, for 181 patients treated with mitoxantrone, vincristine, vinblastine, and prednisone and radiotherapy (P =.7 by log-rank test), 74% versus 84%, respectively, for 54 patients treated with MOPP (P =.4 by log-rank test), and 77% versus 88% for 53 patients treated only with radiotherapy (P =.5 by log-rank test). The 5-year FFS was not statistically different when cutoffs of 5% up to 50% for CD20-positive HRS cells were used. CD20 is expressed by HRS cells in 22% of patients with classical HD but is not associated with different FFS after treatment with equivalent regimens.