We investigated in a retrospective multicenter study the impact of chromosome arm 13q deletion (13q-) as detected by fluorescence in situ hybridization (FISH) on outcome after dose-reduced allografting in patients with multiple myeloma. In 68 of 140 patients, data on chromosome 13q status were available. Most patients included had advanced myeloma. At 2 years, patients with 13q deletion (n = 31) had a shorter event-free (18% vs 42%; P =.05) and overall survival (18% vs 67%; P =.03) than patients without 13q- (n = 37). Patients with 13q- experienced a higher relapse rate (77% vs 44%; P