Abstract Clinical correlative studies have linked 1p36 deletions with worse prognosis in follicular lymphoma (FL). In this study, we sought to identify the critical gene(s) in this region that is responsible for conferring inferior prognosis. BAC array technology applied to 141 FL specimens detected a minimum region of deletion (MRD) of ∼97 kb within 1p36.32 in 20% of these cases. Frequent single-nucleotide polymorphism–detected copy-neutral loss of heterozygosity was also found in this region. Analysis of promoter CpGs in the MRD did not reveal differential patterns of DNA methylation in samples that differed in 1p36 status. Exon sequencing of MRD genes identified somatic alterations in the TNFRSF14 gene in 3 of 11 selected cases with matching normal DNA. An expanded cohort consisting of 251 specimens identified 46 cases (18.3%) with nonsynonymous mutations affecting TNFRSF14. Overall survival (OS) and disease-specific survival (DSS) were associated with the presence of TNFRSF14 mutation in patients whose overall treatment included rituximab. We further showed that inferior OS and DSS were most pronounced in patients whose lymphomas contained both TNFRSF14 mutations and 1p36 deletions after adjustment for the International Prognostic Index [hazard ratios of 3.65 (95% confidence interval, 1.35–9.878, P = 0.011) and 3.19 (95% confidence interval, 1.06–9.57, P = 0.039), respectively]. Our findings identify TNFRSF14 as a candidate gene associated with a subset of FL, based on frequent occurrence of acquired mutations and their correlation with inferior clinical outcomes. Cancer Res; 70(22); 9166–74. ©2010 AACR.