Lymphocyte-predominant Hodgkin disease (LPHD) is a unique clinical entity characterized by indolent nodal disease that tends to relapse after standard radiotherapy or chemotherapy. The malignant cells of LPHD are CD20+ and therefore rituximab may have activity with fewer late effects than standard therapy. In this phase 2 trial, 22 patients with CD20+ LPHD received 4 weekly doses of rituximab at 375 mg/m2. Ten patients had previously been treated for Hodgkin disease, while 12 patients had untreated disease. All 22 patients responded to rituximab (overall response rate, 100%) with complete response (CR) in 9 (41%), unconfirmed complete response in 1 (5%), and partial response in 12 (54%). Acute treatment-related adverse events were minimal. With a median follow-up of 13 months, 9 patients had relapsed, and estimated median freedom from progression was 10.2 months. Progressive disease was biopsied in 5 patients: 3 had recurrent LPHD, while 2 patients had transformation to large-cell non-Hodgkin lymphoma (LCL). All 3 patients with recurrent LPHD were retreated with rituximab, with a second CR seen in 1 patient and stable disease in 2. Rituximab induced prompt tumor reduction in each of 22 LPHD patients with minimal acute toxicity; however, based on the relatively short response duration seen in our trial and the concerns about transformation, rituximab should be considered investigational treatment for LPHD. Further clinical trials are warranted to determine the optimal dosing schedule of rituximab, the potential for combination treatment, and the possible relationship of rituximab treatment to the development of LCL.