Renalase is an enzyme that catabolizes catecholamines such as adrenaline and noradrenaline in the circulation. The human kidney releases this protein into the bloodstream to regulate blood pressure. In kidney transplant recipients, the prevalence of hypertension is 60%-80%.The aim of our study was to assess possible correlations between renalase, blood pressure, and kidney function among 89 prevalent kidney allograft recipients. To obtain normal ranges, we also studied renalase levels in 27 healthy volunteers.Complete blood counts, urea, serum lipids, fasting glucose, and creatinine were measured by standard laboratory methods in the hospital central laboratory. Renalase was assessed with the use of a commercially available kit.In kidney transplant recipients renalase was significantly higher than in healthy volunteers (P<.001). In kidney transplant recipients, renalase correlated with age (r=0.29; P<.05), time after transplantation (r=0.34; P<.01), systolic blood pressure (r=0.28; P<.05), diastolic blood pressure (r=0.27; P<.05), serum creatinine (r=0.49; P<.001), estimated glomerular filtration rate (Chronic Kidney Disease Endemiology collaboration: r=-0.44; P<.0001; Modification of Diet in Renal Disease: r=-0.43; P<.001; Cockcroft-Gault r=-0.39; P<.01), serum phosphate (r=0.34; P<.05). Upon multiple regression analysis renalase was predicted by 70% using age (beta value 0.21, P=0.043), time after transplantation (beta value, 0.22; P=.037), serum creatinine (beta value, 0.50; P=.016), and diastolic blood pressure (beta value, 0.33; P=.027).Renalase is highly elevated in kidney transplant recipients, predominantly dependent on kidney function, which deteriorates with time after kidney transplantation and age. Further studies are needed to establish its putative role in the pathogenesis of hypertension after transplantation and possible novel targeted therapies.