11 mg natural progesterone (P) was administered to 20 healthy menopausal women by means of a nasal spray or intramuscular injection. Circulating P levels were calculated at various times after administration. The spray formulation yielded a CMax of 3.75 ng/ml at TMax = 60 min, the area under the curve (AUC)0–720 being 1,481.6 ± 343. Intramuscular administration yielded a mean Cm3x of 4.137 ng/ml at TMax = 240 min, the AUC0–720 being 2,491.2 ± 540. P absorption was faster through the nasal than through the intramuscular route, but intramuscular administration led to high serum levels for a much longer period.