Urinary growth hormone (GH) excretion was quantitated in 12-hr overnight urine collections obtained from 13 children with complete growth hormone deficiency (CGHD). 6 children with partial growth hormone deficiency (PGHD), 5 children with short stature and normal GH provocation tests (NSC), and 5 normal control children (NC) to investigate whether the measurement of urinary GH can clearly separate the PGHD and CGHD groups from the NSC and NC groups. In addition, the urinary excretion of GH was measured in CGHD after sc injections of 0.1 IU/kg GH three times a week and daily in an attempt to determine the optimal replacement dose. The results were as follows. 1) The 12-hr urinary GH excretion cleary separated the CGHD (1.2+/-1.1 ng/12 hr; range, 0.3-3.1, n=13) and PGHD (3.7+/-2.4 ng/12 hr; range, 0.9-6.8 n=6) groups from the NSC (14.0+/-3.6 ng/12 hr; range, 8.5-18.2 n=5) and NC (12.7+/-5.8 ng/12 hr; range, 6.9-20.8, n=5) groups without any overlap. 2) There were significant difference in 12-hr urinary GH excretion between CGHD and PGHD, but the higher values in CGHD groups overlapped some of the lower values in PGHD group. 3) There were no differencies in 12-hr urinary GH excretion between NC and NSC. 4) A 12-hr urinary GH values less than 6.9 ng/12 hr suggested GH deficiency. 5) The CGHD patients who received o.1 IU/kg GH. sc. daily GH levels within the range of the mean +/-SD in NC. but those who received theree times a week had daily variable urinary GH levels. These results suggest that the measurement of 12-hr nocturnal urinary GH excretion monitering of GH therapy response.