[Complications of pediatric renal transplantation]. Complicações da transplantação renal em idade pediátrica. BACKGROUND: Renal transplantation is the treatment of choice for children with end stage renal disease with positive impact on survival and quality of life. However, some complications affect morbidity and mortality. This study examines the renal transplantation complications profile in pediatric patients (<18 y). MATERIAL AND METHODS: Retrospective analysis of clinical files from renal transplantation patients followed in Pediatric Nephrology Unit from September 1995 to August 2010. Collection of data regarding: demography, end stage renal disease etiology, previous renal replacement therapy, graft loss and death, complications: surgical, infectious and non-infectious (acute and chronic rejection, primary disease recurrence, metabolic and cardiovascular risk factors). Descriptive statistical analysis was performed. RESULTS: 78 children (male: 48.7%), mean age at renal transplantation: 11.7 4.1 years. Previous peritoneal dialysis in 49 (62.6%). Five patients (6.4%) with preemptive renal transplantation. Median follow up: 37.5 months (1-169). Main end stage renal disease etiologies were urologic conditions in 41% and glomerular disease in 28.2%. Infectious complications occurred in 74%: viral: 56.4% (cytomegalovirus in 39.7%); bacterial in 53.8% (mainly urinary tract infections). Non-infectious complications were: 1) cardiovascular risk factors: hypertension in 85.9%, hyperlipidemia in 16.7% and new onset diabetes post transplantation in 7.7%; 2) acute graft dysfunction in 32.1%; graft chronic nephropathy 17.9%; 3) surgical complications 16.7%. In the first month after renal transplantation, surgical complications (11.5%) and bacterial infections were the most prevalent complications. Between the 1st and the 6th month there were more bacterial (34.6% patients) and viral (17.9% patients) infections. From 6th month on, cardiovascular risk factors (89.7% patients) became the more prevalent. There was one death. CONCLUSIONS: The most frequent infections were viral, mainly CMV. Acute graft dysfunction was frequent after the 6th month, probably associated with poor compliance. New morbidities, namely cardiovascular risk factors, are emerging with the evolution of new diagnostic, prophylactic and therapeutic strategies for renal transplantation.