OBJECTIVES: The objective of this study is to analyze the relationship between 12-month renal function and costs in post-kidney transplant patients from the Brazilian Public Health System (SUS) perspective. METHODS: Non-interventional, multicenter, retrospective medical chart review of patients that underwent kidney transplantation. Three years follow-up data on resource use and associated costs from adults (age≥18 years-old at time of transplantation), single kidney only transplants from Jan/2004 to Jan/2005 were collected from 7 transplant centers in Brazilian hospitals. Data were censored on graft loss. Estimated glomerular filtration rates (eGFR) at 12-month post-transplantation were calculated using the abbreviated Modification of Diet in Renal Disease equation and stratified according to the National Kidney Foundation K/Kidney Disease Outcomes Quality Initiative renal function categories. Costs were adjusted to year 2004 at an annual discount rate of 5% and converted to 2010 USD. Case mix group costing approach was used to determine average cost per day of hospitalization, stratified by cause (surgical or clinical complication) and type (general ward, ICU). RESULTS: 498 subjects were eligible for the analysis. Outpatient care resource use and associated costs (excluding costs with immunosuppressive therapy) did not significantly vary among patients in different eGFR categories, with average annual costs ranging from 664 and 921USD in the first year, 194 and 245USD in the second and 129 and 165USD in the third year post-transplantation. However, a trend towards of increasing inpatient costs (p<0.001) and incidence of hospitalization per year with declining of renal function was observed. After 3 years post-transplant, 41% of stage 1 Chronic Kidney Disease (CKD) and 91% of stage 4 patients were re-admited to the hospital at least once incurring an estimated average cost of 1,239 and 3,654USD, respectively. CONCLUSIONS: Renal function, measured by 12-month post-transplant eGFR, is an important determinant of costs of hospitalization in kidney graft recipients.