Autologous hematopoietic stem cell transplantation (AHSCT) in low-grade non-Hodgkin lymphoma (NHL) can result in a prolonged remission, although most patients eventually relapse and die of their disease. We report long-term outcomes of AHSCT for patients with relapsed low-grade NHL. Between May 1983 and 2001, 67 patients with relapsed or refractory stage III and IV low-grade NHL received an AHSCT at the University of Minnesota at a median of 2.3 years (range, 0.4-15.2 years) after diagnosis. At transplantation, 62 patients (92%) were in complete remission (CR) (6%) or partial remission (PR) (86%); 5 (8%) had resistant disease; and 9 (14%) had transformed to a higher-grade NHL. After AHSCT, 32 (49%) of 65 evaluable patients achieved CR, and 26 (40%) achieved PR. Overall survival (OS) was 50% (95% confidence interval [CI], 38%-62%) at 4 years and 33% (95% CI, 20%-46%) at both 10 and 18 years, whereas progression-free survival (PFS) was 28% (95% CI, 17%-39%) at 4 years, 18% (95% CI, 8%-28%) at 10 years, and 14% (95% CI, 4%-25%) at 18 years. Transplant-related mortality in the first 100 days was 3% (95% CI, 0%-7%). Relapse occurred in 62% (95% CI, 48%-75%) at 4 years and 72% (95% CI, 56%-87%) at 10 years. Eleven patients (16%) developed myelodysplastic syndrome/acute myeloid leukemia 1 to 8 years after AHSCT, and 3 (5%) developed solid tumors. In multiple regression analysis, the International Prognostic Index (IPI) score at transplantation was the most significant predictor for both OS and PFS. The median OS has not been reached in patients with an IPI score of 0 or 1 at transplantation (20 of 35 survive 2 to 18 years after AHSCT), whereas it was 2.3 and 1.6 years for IPI scores of 2 and 3, respectively ( P = .002). A good response (CR/PR) to AHSCT (relative risk [RR], 0.4; 95% CI, 0.2-0.9; P = .04) and age <50 years (RR, 0.5; 95% CI, 0.2-0.8; P = .01) were also independently significant predictors of good OS and PFS. We present mature follow-up data (median follow-up, 8 years; range, 2-18 years) of patients undergoing AHSCT for relapsed low-grade NHL and demonstrate extended OS and PFS. Very long-term remissions were seen in nearly 20% of patients. AHSCT remains promising, especially for patients with sensitive relapse and lower IPI scores. Recurrent lymphoma after AHSCT remains the major problem, and prolonged survival is further tempered by a significant risk of post-transplantation second malignancies, including myelodysplastic syndrome/acute myeloid leukemia and solid tumors.