PURPOSE: Efforts to predict the progression of chronic renal failure (CRF) in children, using mathematical models based on transformations of serum creatinine (Scr) concentration, have failed. Error may be introduced by age-related variations in creatinine production rate. Height (Ht) is a reliable reference for creatinine production in children. Thus, Scr, factored for Ht, could provide a more accurate predictive model. We examined this hypothesis. METHODS: The progression of CRF was detected in 63 children who proceeded to end-stage renal disease. Derivatives of Scr, including 1/Scr, log Scr and Ht/Scr, were defined for the period Scr was between 2 and 5 mg/dl. Regression equation were used to predict the time, in months, to Scr > 10 mg/dl. The prediction error (PE) was defined as the predicted time minus actual time for each Scr transformation. RESULT: The PE for Ht/Scr was lower than the PE for either 1/Scr or log Scr (median: -0.01, -2.0 and +10.6 mos respectively; p < 0.0001). For children with congenital renal diseases, the PE for Ht/Scr was also lower than for the other two transformations (median: -1.2, -3.2 and +8.2 mos respectively; p < 0.0001). However, the PE's for children with glomerular diseases was not as clearly different (median: +0.9, +0.5 and +9.9 respectively). In children <13 yrs, PE for Ht/Scr was the lowest, while in older children, 1/Scr provided the lowest PE, but not significantly different from that for Ht/Scr. The logarithmic transformation tended to predict a slower progression of CRF than actually occurred. CONCLUSION: Scr, factored for Ht, appears to be a useful model to predict the rate of progression of CRF, particularly in the prepubertal child with congenital renal disease.