In 1997, the approval of the anti-CD20 antibody rituximab heralded a new era of combined immunochemotherapy for the treatment of malignant lymphoma. Until then, a combination of cyclophosphamide, vincristine, doxorubicin, and prednisone (CHOP) had been the standard of treatment for aggressive B-cell lymphoma for more than 25 years. The addition of rituximab led to an impressive improvement of response rates and survival outcomes in patients with follicular and diffuse large B-cell lymphoma (DLBCL) that has been confirmed in several randomized trials. Remaining challenges in the rituximab era are the identification of the optimal chemotherapy partner with respect to synergistic effects, as well as to the lack of interference with its effector mechanisms. Finally, the question of the optimal dosage and schedule of rituximab has to be addressed in well-designed randomized trials. The outcome of patients relapsing after a rituximab-containing induction regimen is dismal even with high-dose therapy and autologous stem cell transplantation (ASCT). For these patients new modalities of second-line therapy are urgently warranted.