Sex steroid levels in women vary with increasing age from the age of 70 years (70+). Whether this reflects change within individuals with age or a survival advantage is not known. This study aimed to determine the stability of circulating sex steroids and SHBG over time in individual women aged 70+.A prospective cohort study.400 women, aged 70+ not using any sex steroid, anti-androgen/estrogen or glucocorticoid therapy.Sex steroid concentrations, measured by liquid chromatography-tandem mass spectrometry and sex hormone binding globulin (SHBG) by immunoassay, in paired blood samples drawn 3 years apart and analysed together.400 women, median (IQR) age 78.0 (8.6) years, were included in the analysis. Mean testosterone concentrations were statistically significantly higher in follow-up samples compared with baseline. The change was modest (mean change 31 pmol/L, 95% confidence interval (CI) 2.4 to 59.8; p= 0.034) and an increase was not observed in all women. There was a statistically significant decline in mean body mass index (mean change -0.4 kg/m2 , 95%CI 0.6 to -0.3; p<0.001) and a significant increase in the mean serum SHBG concentration (mean change 4, 95%CI 3 to 5; p<0.001). The change observed in testosterone was not explained by the observed change in SHBG. There was no significant change in the mean estrone or dehydroepiandrosterone concentration.Testosterone concentrations in women aged 70+ were more likely to increase than decrease. Whether increasing testosterone concentrations in older women confer a survival advantage needs investigation.