Hypoxia inducible factors (HIFs) activate oncogenic pathways, while thioredoxins (Trx), including Trx1 and Trx reductases-1 and -2 (TrxR1 and TrxR2), promote HIF-alpha stabilization. In immunoblotting studies in lymphoma cell lines we found that Raji and SUDHL4 cells exhibited normoxic HIF-2alpha protein stabilization. Five cell lines showed increased TrxR1 expression, while only Namalwa, HF1 and SUDHL4 had Trx1 and TrxR2 activation. Tissue microarrays in diffuse large B-cell lymphoma (DLBCL) and follicular lymphoma (FL) identified different HIF expression among histological subgroups (e.g. 44% DLBCL vs. 11% of FL cases with moderate-to-high expression of HIF-1alpha and HIF-2alpha, P = 0.0017). These data demonstrate that HIF and the thioredoxin family are abnormally activated in lymphoma.