The purpose of this study was to identify clinical, nutritional, and laboratory factors associated with the rate of progression of chronic renal insufficiency among children and adolescents admitted to a pre-end-stage renal failure (ESRF) interdisciplinary program. Sixty-two children and adolescents aged 2 months to 19 years with chronic renal failure on conservative management were prospectively followed from 1990 to 1999. The following variables were analyzed: age at admission, sex, race, blood pressure, primary renal disease, Z scores for weight and height, glomerular filtration rate (GFR), urea, and presence and degree of proteinuria. Progression to ESRF was assigned as a dependent variable. The analysis was conducted in two steps. In a univariate analysis, variables associated with ESRF outcome were identified by the log-rank test. Then, the variables that were significantly associated with adverse outcome were included in a multivariate analysis. This analysis, using the Cox proportional hazards model, was performed to identify variables that were independently associated with a worse prognosis. Only variables that remained independently associated with adverse outcome were included in the final model. Twenty-one (34%) patients evolved to ESRF during a median follow-up of 43 months. Two variables were identified as independent predictors of progression to ESRF: GFR under 30 ml/min (RR=3, 95% CI=1.7-5.3, P=0.0001) and severe proteinuria (RR=3.1, 95% CI=1.2-7.6, P=0.01). The combination of two factors-GFR lower than 30 ml/min and presence of severe proteinuria on admission-was an independent indicator of adverse outcome in children and adolescents with chronic renal insufficiency who were conservatively managed.