Background: High altitude is associated with hypobaric hypoxia and increased risk for microalbuminuria in adults. We hypothesized that healthy adolescents at higher altitude might have an increased frequency of microalbuminuria in comparison with a group of adolescents living at sea level. Methods: We evaluated the presence of microalbuminuria in adolescents at sea level (n=68, altitude 130 meters) and at high altitude (n=114, altitude 3200 meters) living in Peru. Each subject was evaluated for body mass index, Blood Pressure, microalbuminuria, proteinuria, hematuria and leukocyturia in a first morning urine sample. Subjects with a positive test for microalbuminuria underwent repeat testing one or two weeks after the initial screening. Results: Subjects at sea level and high altitude had similar age, weight, height and blood pressure (p=NS). Microalbuminuria without any other urinary abnormality, was higher in the first screening among adolescents residing at high altitude compared to those living at sea level (42 vs15, p: 0.0215). In the second screening the results were similar in both groups (31 vs 11, p: 0.0879). Conclusion: Persistent microalbuminuria was observed in more than one-quarter of adolescents living at high altitude. This study suggests that subtle renal injury may occur early in subjects living at high altitude.