We report two patients with primary cutaneous B-cell lymphoma who were treated with rituximab, a new anti-CD20 monoclonal antibody. The first patient, who had a diffuse large B-cell lymphoma of the lower leg, achieved an 85% improvement. The second patient, who had a primary cutaneous B-cell lymphoma, which had undergone high-grade transformation and systemic spread, achieved a minor response of approximately 30%. Both patients subsequently relapsed. The first patient achieved complete clearance with a second course of rituximab given with systemic chemotherapy, but again relapsed. Treatment with rituximab has been reported to produce response rates of 48% in relapsed systemic low-grade or follicular lymphoma, but there are no previous reports of the use of rituximab in primary cutaneous B-cell lymphoma.