We performed a case-control study in renal transplant patients between 1998 and 2003 to identify risk factors for arterial hypertension over the medium term in pediatric patients undergoing renal transplantation. Three years after transplant, patients were classified into hypertensive or control groups. The following risk factors were analyzed: hypertension before transplant, glomerular filtration rate at sixth posttransplant month, acute rejection episodes, renal artery stenosis, accumulated prednisone and calcineurin inhibitor doses, presence of native kidneys, donor type (living or cadaver), body mass index at 1 year posttransplant, and glomerular disease as renal insufficiency etiology. Of 161 transplants, 124 fulfilled the inclusion criteria; 63 were hypertensive, and 61 were controls. Univariate analysis showed hypertension before transplant (52/63 vs. 27/61, p < 0.001), glomerulopathies (23/63 vs. 12/61, p = 0.001), glomerular filtration rate at 6 months (71 +/- 18 vs, 80 +/- 18 ml/min per 1.73 m(2), p = 0.003) as risk factors. A tendency to statistical significance was observed with regard to body mass index (SDS) in the first year (0.40 +/- 1.10 vs, 0.04 +/- 1.10, p = 0.072). Multivariate analysis showed statistical significance concerning previous hypertension and glomerular filtration rate at 6 months. Hypertension before transplant and early graft function are the major risk factors for hypertension in the medium term following renal transplant.