The concentration of estrone, estradiol, and cstriol in β-glucuronidase and sulfatase treated plasma and of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) in serum from blood collcctcd daily throughout a sub-stamial portion of a normal menstrual cycle have been determined. The patterns found are compatible with the cyclical changes expected on the basis of earlier studies of LH and FSH In serum, urinary estrogens, and unconjugatcd estrogens in plasma, with the midcycle peak of estradiol preceding those of the gonadotropins. © 1974 The American College of Obstetricians and Gynecologists.