We investigated the toxicity and efficacy of the chimaeric anti-CD20 antibody rituximab in combination with standard-dose chlorambucil in newly diagnosed and relapsed/refractory indolent B-cell lymphoma patients. A total of 29 patients (15 newly diagnosed and 14 relapsed/refractory) with low-grade or follicular B-cell non-Hodgkin's lymphoma (NHL) were included in this phase II study. Therapy consisted of chlorambucil 6 mg/m2/d for 6 consecutive weeks in combination with a standard 4-weekly rituximab administration schedule in the induction phase. Patients responding to the induction therapy received four additional cycles with chlorambucil (6 mg/m2/d for 2 weeks/month) plus rituximab (once a month). Twenty-six patients (89%) completed the treatment; only one patient discontinued treatment because of haematological toxicity. At the end of the study, the dose of chlorambucil had to be reduced in seven patients (27%) and six patients (23%) required a delay in further treatment, as a result of toxicity during consolidation therapy. Only one patient was withdrawn from the study because of progressive disease; the 27 patients evaluable for response at the end of consolidation achieved a clinical response (63% complete response and 26% partial response). A significant CD4+ and CD56+ depletion was observed after induction and during consolidation therapy; two herpes zoster virus infections and one perianal abscess represented major infectious morbidities registered during the study. Based on our preliminary data, the combination of chlorambucil with rituximab seemed to be well tolerated and active. Its definitive role in the treatment of low-grade NHL should be further evaluated in randomized trials.