The expression of lactate dehydrogenase 5 (LDH5), the major LDH isoenzyme sustaining the anaerobic transformation glycolysis was examined in B-cell non-Hodgkin lymphomas. Multi-tissue slides obtained from patients with diffuse large B-cell lymphomas (DLBCL; 95 cases), follicular lymphomas (FL; 49 cases) and from non-neoplastic lymph nodes (48 cases) were used for immuhistochemical analysis. High LDH5 expression (cytoplasmic and nuclear) was noted in 79/95 and 29/49 cases of DLBCL and FL, respectively (p = 0.002). No expression was noted in non-neoplastic lymphocytes. In DLBCL, LDH5 expression was significantly related to hypoxia inducible factor HIF1alpha, HIF2alpha, vascular endothelial growth factor (VEGF) and phosphorylated vascular endothelial growth factor receptor 2 (VEGFR2/KDR) expression. In FL, however, a significant relation was confirmed with pVEGFR2/KDR and HIF2alpha. FL cases with the highest microvessel density were those, which lacked both LDH5 and VEGF expression. It is concluded that LDH5 is highly upregulated in B-cell non-Hodgkin lymphomas and is in direct relation to HIFs expression. LDH5 expression is linked with activated VEGFR2/KDR expression in both lymphoid lesions.