The role of involved field radiation therapy (IF-RT) after high dose chemotherapy (HDC) with autologous stem cell transplantation (ASCT) for non-Hodgkin's lymphoma (NHL) has not been conclusively defined. It has been hypothesized that HDC might obviate the need of consolidative IF-RT. A retrospective matched-pair analysis of patients undergoing HDC and ASCT with or without consolidative IF-RT has been performed. Fifteen patients treated with IF-RTafter ASCTwere compared with 15 patients without IF-RT, identical for histology, stage and treatment response to HDC/ASCT as well as comparable for international prognostic index (IPI) score, age and gender. After a mean follow-up time of 65±45 months, none of the patients with consolidative IF-RT following HDC and ASCT relapsed within the involved field compared to six patients without consolidative IF-RT (IF-failure risk at 5 years: 0% vs. 40%;p<0.005). In most of the cases, local relapse was seen in patients with bulky disease. The 5-year risk for loco-regional failure was 7% after consolidative IF-RT and 38% in patients without IF-RT (p=0.02) while the 5-year risk for developing distant recurrences was similar in both groups (30% with IF-RT vs. 35% non-IF-RT;p=0.7). Overall survival at 5 years was similar with 79% (IF-RT) and 65% (non-IF-RT), respectively (p=0.2). Acute toxicity due to consolidative IF-RT was mild in most cases and severe acute toxicity was noticed in only one patient (7%). Long-term toxicities observed after IF-RT were coronary artery disease, secondary malignancy unrelated to the RT-field, angina abdominalis, hypothyroidism and teeth decay. Recurrence of NHL at sites of macroscopic disease remains common despite HDC. IF-RT achieves excellent local regional control and consolidative IF-RT after ASCT seems indicated, particularly in patients with bulky disease. In the absence of a prospective randomized trial and proven impact on survival rates, IF-RT can be recommended as an option post-ASCT to enhance local disease control.