Plasma androstenedione (A) and oestrone (E1) levels were measured by radioimmunoassay in a group of 78 healthy women who had undergone a natural menopause. Of this total, 23 were symptomless (Group 1), 39 presented with a moderate climacteric syndrome (Group 2) and 16 had a severe climacteric syndrome (Group 3). The average body weight was found to be significantly higher in Groups 2 (P less than 0.01) and 3 (P less than 0.05), than in Group 1, but the age distribution and number of years since the menopause were similar in all three groups. Nevertheless, significantly lower levels of A (0.75 +/- 0.06 ng/ml, P less than 0.01, in Group 2; 0.24 +/- 0.05 ng/ml, P less than 0.001, in Group 3) and E1 (20.80 +/- 2.18 pg/ml, P less than 0.05, in Group 2; 12.22 +/- 1.65 pg/ml, P less than 0.001, in Group 3) were observed in the women with climacteric symptoms than in those with no symptoms (A = 1.08 +/- 0.08 ng/ml, E1 = 27.73 +/- 2.22 pg/ml in Group 1). Since, after the menopause, the concentrations of A and E1 in the plasma represent the most important source of oestrogens, these results suggest that climacteric symptoms are related to oestrogen deficiency which is secondary to low A production.