PURPOSE: The long-term results after using the iliotibial band autograft (ITB) in anterior cruciate ligament (ACL) reconstruction are not fully known. If equal in quality to conventional methods, the ITB graft could be a useful alternative as a primary graft, in revision surgery or multi-ligament reconstruction. The purpose is to assess whether the ITB autograft is a long-term reliable alternative to the bone-patella-tendon-bone (BPTB) autograft, using a prospective randomized controlled trial design. METHODS: From 1995 to 1996, sixty patients scheduled for primary ACL reconstruction were included in a prospective randomized controlled trial. Three senior knee surgeons, experienced in both types of ACL surgery, performed all the operations. A standardized and supervised rehabilitation programme was used for both groups for 6 months. Thirty patients received the ITB reconstruction, and 30 received the BPTB reconstruction. Forty-nine participated at follow-up in 2010 (82%). Primary outcome was the failure rate after ACL reconstruction. Secondary outcomes were knee injury osteoarthritis outcome score (KOOS) [pain, symptoms, Sport/Rec, quality of life (QOL), daily living function], Tegner activity scale, anterior knee pain-score, Lysholm score, Rolimeter laxity, extension deficit, single hop and crossover hop for distance. RESULTS: At 15-year follow-up, no significant difference existed between the groups. Graft failure occurred in 4 ITB subjects (16%) and 3 BPTB subjects (13%). KOOS (Sport/Rec) for the ITB group was 75 and 73 for the BPTB group. The KOOS (QOL) was 72 and 68 for the ITB group and BPTB group, respectively. CONCLUSION: Similar graft failure rates and KOOS were found when comparing ITB- and BPTB-operated individuals, at 15-year follow-up. The ITB graft had equal long-term clinical results compared to the BPTB graft and is recommended as a reliable alternative autograft for ACL reconstruction. LEVEL OF EVIDENCE: Therapeutic studies, Level I.