Two female patients suffering from postoperative tetany had their attacks chiefly at the menstrual periods. Administration of ovarian hormones led to the following conclusions: 1. 1. The ovaries may influence the neuromuscular excitability of the body. 2. 2. In these patients the ovarian hormones did not depress the blood calcium level and they did not act as an antagonist to dihydrotachysterol. On the contrary, in one patient the dihydrotachysterol need seemed to be decreased. 3. 3. The clinical benefits noted in these two patients justifies further carefully controlled study and use of ovarian hormones in similar cases. Since this article was submitted for publication the patients have received no sex hormone therapy. The patient in Case 11 has had two moderately severe attacks of tetany.