The plasma concentrations and episodic fluctuations of immunoreactive FSH and LH as well as the pituitary sensitivity to LH-RH stimulation were evaluated in post-menopausal women. The subjects were divided into 4 groups according to age. Group 1: 60-70 years old (n= 11), group 2: 70-80 years old (n=22), group 3: 80-90 years old (n=31) and group 4: 90-100 years old (n = 8). Standards used in gonadotrophin radioimmunoassays included the LER-907 preparation and a pooled post-menopausal serum. Since it was found that circulating gonadotrophins have an immunological pattern different from that shown by the pituitary preparation, the results were expressed in mIU/ml calculated accordingly to the immunological behaviour of pooled post-menopausal sera. The mean (\m=+-\se) plasma levels of FSH (mIU/ml) were: group 1: 105.9 \ m=+-\9.5, group 2: 149.3 \ m=+-\10.5, group 3: 124.8 \ m=+-\7.1 and group 4: 149.4 \ m=+-\25.3. The mean (\ m=+-\se) plasma levels of LH (mIU/ml) were: group 1: 81.9 \ m=+-\12.5, group 2: 95.4 \ m=+-\ 9.9, group 3: 84.3 \ m=+-\ 7.7 and group 4: 113.5 \ m=+-\ 19.1. No statistically significant differences were observed among the 4 groups. One patient from each group was randomly selected in order to evaluate their LH and FSH episodic release as well as their pituitary responsiveness to