Anti-cluster of differentiation 20 (CD20) monoclonal antibodies (mAbs) have shown promise in follicular lymphoma (FL) as post-induction therapy, by enhancing antibody-dependent cellular cytotoxicity (ADCC). However, cytotoxic cells are reduced after this treatment. We hypothesised thatex vivoexpanded lymphokine-activated killer (LAK) cells administered to FL-remission patients are safe and improve anti-CD20 efficacy. This open, prospective, phase II, single-arm study assessed safety and efficacy ofex vivoexpanded LAK cells in 20 FL-remission patients following rituximab maintenance. Mononuclear cells were obtained in odd rituximab cycles and stimulated with interleukin 2 (IL-2) for 8 weeks, after which >5 x 10(8)LAK cells were injected. Patients were followed-up for 5 years. At the end of maintenance, peripheral blood cells phenotype had not changed markedly. Natural killer, LAK and ADCC activities of mononuclear cells increased significantly after recombinant human IL-2 (rhIL-2) stimulation in all cycles. Rituximab significantly enhanced cytotoxic activity. No patients discontinued treatment. There were no treatment-related serious adverse events. Three patients had progressed by the end of follow-up. After a median (interquartile range) follow-up of 59.4 (43.8-70.9) months, 85% of patients remained progression free. No deaths occurred. Quality-of-life improved throughout the study. Post-induction LAK cells with rituximab seem safe in the long term. Larger studies are warranted to confirm efficacy.