GH levels were measured every 30 min during sleep over 9 h in 10 patients with Turner's syndrome ranging in age from 10.6-18.9 yr (mean, 15.0 +/- 2.7 yr) and in 12 controls matched for bone age, all of whom had normal GH responses to an orally administered dose of clonidine. We found no significant difference in the mean 9-h overnight GH concentration between groups. The overnight GH concentration was 3.8 +/- 2.2 micrograms/L (mean +/- SD) in Turner's syndrome patients and 4.5 +/- 2.4 micrograms/L in the control group. Total GH output (205.4 +/- 118.7 vs. 251.4 +/- 122.0 U), total number of nocturnal GH pulses (2.4 +/- 0.8 vs. 2.9 +/- 0.7), and mean peak GH response during nocturnal sampling (13.0 +/- 7.4 vs. 13.2 +/- 3.3 micrograms/L) were not different in the children with Turner's syndrome and the controls. We conclude that pubertal age patients with Turner's syndrome secrete GH normally and do not have any abnormality in GH regulation.