Advanced stages of follicular lymphoma are deemed incurable by conventional approaches. Immunotherapy with the humanised monoclonal anti-CD20 antibody rituximab represents a new therapeutic option. The aim of our study was to determine the effectiveness and safety of rituximab in the consolidation setting of first-line treated patients with follicular lymphomas. Thus the goal was first to reduce tumour burden using the CHOP regimen as induction treatment followed by consolidation with rituximab administered on a standard 4 wk schedule at a dosage of 375 mg m-2 body surface area. Between August 1998 and April 2001, 41 patients were enrolled in the study. All patients were evaluable with regard to tumour response and toxicity. The overall remission rate in the intent-to-treat analysis was 100%. On subgroup analysis, 20 [83% (95% CI: 63-95%)] of the 24 patients with grade 1 or 2 histology entered complete remission (CR), in 10 cases (42%) after additional rituximab therapy. Rituximab thus led to CR in 10/14 patients [71% (95% CI: 42-92%)] who had merely achieved partial remission (PR) with CHOP. Of 16 evaluable patients with grade 3 histology (excluding one patient achieving CR on CHOP who refused further treatment with rituximab), 15 [94% (95% CI: 63-97%)] achieved CR, 13 (81%) of these while still receiving CHOP. Two of the three patients achieving only PR on CHOP entered CR following rituximab. Thirty-four patients (83%) continued to be in remission during a median follow-up period of 24.3 (9-40) months. Our data suggest that the use of rituximab for consolidation after CHOP may improve CHOP-induced remission and thus increase the CR rate. Furthermore, it was accompanied by a reduced rate of infusion-related side-effects.