To verify some animal experimental results in humans, we have studied urinary epidermal growth factor (EGF) excretion in normal children as well as children with acute renal failure (ARF). Urinary EGF excretion was expressed as a ratio of urinary EGF to urinary creatinine concentration (EGF/Cr) for random and 24-h urine, and a daily total urinary EGF for 24-h urine. The highest urinary EGF/Cr in children was found at 1 mo to 3 y of age. There was a highly significant correlation between random urine EGF/Cr and 24-h urine EGF/Cr (r= 0.92,p< 0.001), whereas no correlation of urinary EGF/Cr with daily total urine EGF was found. During the course of ARF, a decline in urinary EGF/Cr from the period before peak serum creatinine to the period after the declination of serum creatinine was noted (p= 0.013,n= 13, by repeated measure analysis), with a constant low daily total urine EGF (pvalue not significant). However, a rise in both urinary EGF/Cr and daily total urine EGF was found between the period of serum creatinine decline and the period of completely normal serum creatinine(p< 0.001). Serum EGF remained unchanged throughout the course of ARF. These results suggest1) the possible role of EGF in renal growth or maturation during the first 2 or 3 y of life,2) the possible renal origin of human urinary EGF, and3) decreased urinary EGF excretion in children with ARF. In particular, EGF/Cr is not a reliable indicator for the expression of actual urinary EGF excretion in ARF. Instead of urinary EGF/Cr, urinary EGF concentration may be used to predict the daily total urinary EGF excretion during ARF. These results provide the pattern of urinary EGF excretion during ARF in children and may be of help for further clinical studies.Abbreviations: ARF,acute renal failure;EGF,epidermal growth factor;EGF/Cr,ratio of EGF to creatinine