Eighty neonates, including 14 full-term, 31 premature, 27 twin or triplet, 6 small-for-gestational-age, and 2 infants with hyperthyroidism, were evaluated. The urinary epidermal growth factor/creatinine ratio (EGF/Cr) on the 1st postnatal day was not statistically different among full-term, premature, multiple-pregnancy, and small-for-gestational-age infants (F = 1.06, p = 0.6). There was no difference in urinary EGF/Cr between the 1st postnatal day and the 7th day (p = 0.4 by paired t test). The urinary EGF/Cr was not correlated with the serum thyroid-stimulating hormone level (r = -0.162, n = 60, p = 0.21), but showed a positive correlation with serum total T3 (r = 0.526, n = 60, p < 0.001) and with serum total T4 (r = 0.460, n = 60, p < 0.001). The correlation between urinary EGF/Cr and serum free T4 was even much better (r = 0.727, n = 25, p < 0.001). These results implicate that thyroid hormone may play a role in regulating urinary EGF excretion.