This report describes three cases of posttransplant lymphoproliferative disorder (PTLD) in multivisceral/small bowel transplant patients treated with rituximab (anti-CD20 monoclonal antibodies). In two cases (one of which was a B-cell lymphoma) a good response to therapy was achieved. A third case (with polymorphic PTLD with low CD20 expression) developed a refractory rejection and PTLD was still documented on graftectomy. Rituximab was well tolerated, and a reduction of Epstein-Barr virus (EBV) viral load was documented by quantitive competitive-EBV polymerase chain reaction. Efficacy of therapy needs to be assessed in controlled studies.