BACKGROUD: The R98 trial explores the addition of irinotecan to a 5-fluorouracil (5-FU) plus leucovorin (5-FU/LV) adjuvant regimen in optimally resected stages II-III rectal cancers. We report the updated long-term results. Disease-free survival (DFS) was the primary end point. PATIENST AND METHODS: Between March 1999 and December 2005, 357 patients were randomized: 178 in 5-FU/LV and 179 in LV5-FU2 + irinotecan arm. The trial was stratified by control arm: Mayo Clinic regimen or LV5-FU2 regimen. RESULTS: Three hundred and fifty-seven randomized patients were evaluable for efficacy. With a follow-up of 156 months, the DFS was in favour of experimental arm but did not reach statistical significance [hazard ratio (HR) = 0.80, P = 0.154]. The same was observed for overall survival (OS) (HR = 0.87, P = 0.433). The 5-year DFS was 58% in the control arm and 63% in the experimental arm. The 5-year OS was 74% in the control arm and 75% in the experimental arm. Patients allocated to the experimental arm had more grade 3-4 neutropenia when compared with the LV5-FU2 arm (33% versus 6%, P = 0.03), but not when compared with the Mayo Clinic arm (33% versus 36%, P = 0.84). Grade 3-4 diarrhoea tended to be higher in the experimental arm, but analyses stratified by control arm or by radiotherapy failed to show significant differences across strata (test for interaction P = 0.44). CONCLUSION: Even though a benefit of irinotecan in subgroups of patients cannot be excluded, due to early termination and lack of power, the study does not support the addition of irinotecan to 5-FU/LV in routine in patients with resected stage II-III rectal cancer.