Serum levels of carboxyterminal propeptide of type I procollagen (PICP) and aminoterminal propeptide of type III procollagen (PIIINP) can be used as markers of bone formation and the evaluation of children with growth disorders. We measured the serum levels of these collagens with radioimmunoassay in 24 children aged between 4 and 14 years with chronic renal failure (CRF; n = 12 dialysis, n = 12 nondialysis) and 12 age-matched healthy controls, to find out whether these parameters have a prognostic or therapeutic value in monitoring the growth retardation in CRF. Mean serum PIIINP levels in the dialysis patients were higher than in the control group; the difference between the groups was statistically significant (p < 0.05). It seemed that the pubertal stage of the patients did not affect the levels of PICP and PIIINP. There was no significant correlation between PICP and PIIINP in any patients. Neither PICP nor PIIINP correlated with the height z-score or bone age. It was concluded that the increased serum PIIINP levels in renal patients might be accepted as a poor prognostic factor leading to progressive renal failure and end-stage renal disease. Further investigations into the effects of these collagens on growth failure associated with CRF are needed.