In studies on plasma gonadotropins in patients with the syndrome of gonadal dysgenesis, we observed significant variations in the concentrations of plasma LH in serial samples. To examine this observation further, plasma gonadotropins were determined every 15 min for 2–5 hr in 7 patients with gonadal dysgenesis (10–20 yr old). All subjects were sexually immature and were studied before treatment with estrogens. Six of 7 had increased plasma FSH values and 5/7 had increased LH values. Plasma LH (LER 960) and FSH (LER 869) concentrations were measured by radioimmunoassay. Significant episodic increases in plasma LH were found in all subjects with increased baseline values. Fourteen LH peaks occurred during a total of 20 hours of monitoring. The changes in plasma FSH usually paralleled the changes in LH, but the FSH peaks were broader and were statistically significant in only one patient. We conclude that LH is secreted episodically in adolescent patients with primary hypogonadism.