Four consecutive menstrual cycles were studied in six healthy parous women. A solvent mixture comprising propylene glycol:ethanol:water (3:3:4) was sprayed intranasally daily using a glass atomizer between days 5 and 24 of the first (control) menstrual cycle. NET was dissolved in the solvent and similarly administered at a daily dose of 100 mcg during the second and third menstrual cycles. Nasal sprays were not administered during the fourth post-treatment cycle. Blood samples were taken during four consecutive cycles between days 8 and 15 and again between days 20 and 24 of the cycle to estimate levels of estradiol (E2), FSH, LH and progesterone (P). These studies revealed that nasal sprays of NET were well accepted and that no adverse clinical effects or menstrual disturbances occurred. NET inhibited ovulation in one cycle. The E2-induced mid-cycle rise in FSH and LH was either suppressed or inhibited in nine out of the 12 treated cycles. P levels in three treated cycles were indicative of luteal inadequacy. These endocrine effects of NET persisted into the post-treatment cycle in two cases.