Severe hypomagnesemia has been reported with use of proton-pump inhibitors (PPIs). We assessed the effect, if any, of PPI use on serum magnesium level in a cross-sectional analysis of a large published cohort of renal transplant recipients (RTRs). Between February 2004 and February 2006, 512 consecutive prevalent RTRs were enrolled at two university hospitals in Belgium (Brussels and Ghent). Serum creatinine was 1.5 ± 0.7 mg/dl, and estimated glomerular filtration rate (eGFR) 53 ± 19 ml/min/1.73 m(2). Mean (and median) magnesium level was 1.91 ± 0.23 mg/dl. PPIs were prescribed in 20 % (n = 101) of cases. At multivariable analysis, PPI use was not an independent predictor of serum magnesium level or hypomagnesemia. The independent predictors of a lower serum magnesium level were the use of tacrolimus, cyclosporin and sirolimus, the absence of use of mycophenolate mofetil, lower levels of parathyroid hormone and higher eGFR. This study is the first to analyze the potential impact of PPIs on magnesium level in a large, representative cohort of RTR patients. Our results suggest that PPIs may be used without particular fear of favoring hypomagnesemia-related side effects in RTRs, an important finding in a population at high risk of hypomagnesemia.