Somatic growth follows proliferation of cells and deposition of material in the extracellular matrix. This process takes place in both bone and soft tissue. The carboxyterminal propeptide of type I procollagen (PICP) and aminoterminal propeptide of type III procollagen (PIIINP) are the major extracellular components of these. We measured serum levels of these procollagens by radioimmunoassay (RIA) in 23 children (aged 6.6 to 12.2, mean: 9.9) with growth retardation (seven of these with growth hormone (GH) deficiency) and in 14 healthy children (aged 6.0 to 12.8, mean: 8.8). A statistically significant difference was revealed between the PICP levels of GH-deficient children and healthy children (P < 0.05). But there was only a marginally significant difference between PICP concentrations of the GH-deficient and the non-deficient (GH-normal) retarded group (P = 0.05). No correlation was observed between PICP, PIIINP and age, height z-score. Our data have demonstrated that the measurement of serum PICP levels may be useful in the diagnosis of GH deficiency.