Background: Renal impairment is increasingly reported among HIV-Infected patients and has been associated to an increased chance of cardiovascular disease and death. Therefore, early identification of this problem could help to reduce morbidity and mortality among these individuals. The objective of the study was to determine the prevalence and associated factors with mild decrease in renal function of HIV-infected patients on highly-active antiretroviral therapy (HAART) and undetectable viral load in Brazil. Methods: Individuals between 18-70 years of age with time on HAART ≥ 12 months, viral load < 50 copies/mm 3 , and CD4 ≥ 200 cells/mm 3 , were consecutively enrolled at the outpatient clinic of Hospital de Clínicas de Porto Alegre, Brazil. Exclusion criteria were chronic kidney disease, pregnancy and known hepatic disease. Renal function was assessed by the Chronic Kidney Disease Epidemiology Collaboration equation. Mild decrease in renal function was defined as an estimated glomerular filtration rate between 89-60 mL/min/1.73m 2 , for a period of at least 3 months. Results: From the total of 213 enrolled volunteers, 193 were included in the final analysis. The mean age was 41.5 years, 102 were men (52.6%), and 156 (80.4%) were euro-descendants. Mild renal decline was diagnosed in 33.5% of the patients. Every other year of life (RR=1.05, 95%CI 1.03-1.06, p<0.001) and being euro-descendant (RR=1.94; 95%CI 1.07-3.78; p=0.049) were associated to mild decreases, whereas high body mass index (BMI) (RR=1.04, 95% CI 1.013-1007, p<0,001) was associated to normal function. Conclusions: Mild decrease in renal function was extremely common and more than expected in our cohort (33.5%) which deserves further attention while assisting HIV-positive individuals. J o urnal o f A ID S & Cli n ic a l R es earc h