A retrospective study was performed to assess the outcome of patients with diffuse large B cell lymphoma (DLBCL) who did not achieve complete response or who relapsed before and after the use of rituximab. Clinical features and outcome of 816 (425 M/391 F; median age 63 years) patients diagnosed from 1991 to 2001 (pre-rituximab era, N = 348) and from 2002 to 2012 (rituximab era, N = 468) in a single institution were evaluated. Five hundred fifty-three patients achieved complete remission (CR), 57 partial response (PR), and 206 were refractory with a median overall survival of 15, 1.5, and 0.4 years, respectively. Patients receiving rituximab had lower risk of refractoriness or relapse. In primarily refractory and PR patients, there was not a difference in survival depending on whether patients received or not rituximab-containing frontline treatment. Early death rate was 11%, including 3.6% due to infectious complications. Rituximab did not modify these figures. In the relapse setting, 5-year survival from relapse was 25% for patients who never received rituximab, 54% for those who received rituximab only at relapse, and 48% for those treated with immunochemotherapy both as frontline and at relapse. In conclusion, relapsed/refractory patients with DLBCL show poor prognosis despite the use of frontline immunochemotherapy. New therapeutic approaches are needed in this group of patients.