Cross sectional and longitudinal studies of plasma FSH and LH in 58 patients, age 2 days of 20 yr, with the syndrome of gonadal dysgenesis show a diphasic pattern of gonadotropin secretion. The mean basal plasma FSH level is 43 plus or minus 7 (SE) ng/ml (LER-869) in patients from 2 days to 4 yr, which is strikingly elevated. Thereafter, a decline in plasma FSH to a mean level of 4 plus or minus 0.7 (SE) ng/ml occurs between 4 and 10 yr, followed by a rise after 10 yr to 61 plus or minus 4 (SE) ng/ml. The pattern of LH (LER-960) secretion is qualitatively similar to that of FSH, although quantitatively the values for LH are 1/3 to 1/10 those for FSH. The similarity of pattern of gonadotropin secretion observed between patients with gonadal dysgenesis and normal children suggests that gonadal function does not play a decisive role in the pattern of gonadotropin secretion from infancy through adolescence, but exercises striking effects on the quantity of gonadotropin secreted.