To determine the effects of puberty and estrogen priming on the GH response to standardized treadmill exercise and arginine-insulin in normal boys and girls, we performed tests in 84 normal children (41 girls and 43 boys) representing all stages of puberty. A subset of the prepubertal children received the tests twice, with or without the administration of ethinyl estradiol (40 micrograms/m2 daily) for 2 days before the tests. The peak GH response to the three tests increased significantly with pubertal stage (r = 0.57; P < 0.0001), but did not differ between boys and girls at the same stage. With advancing puberty, the percentage of normal children who failed to attain a GH level greater than 7 micrograms/L during any of the three tests declined from 61% at pubertal stage 1 to 44% at stage 2, 11% at stage 3, and 0% at stages 4 and 5. Administration of estrogen to the prepubertal subjects raised the normal range for the peak GH response to the three tests from 1.9-20.3 to 7.2-40.5 micrograms/L. We conclude that both puberty and estrogen administration significantly increase the peak GH response to exercise, arginine, or insulin in normal subjects. Moreover, the conventional criterion that the peak GH response to three stimulation tests should exceed 7 micrograms/L was applicable in our study only to subjects who had attained pubertal stage 4 or 5 or who had received estrogen administration.