This study was carried out to determine whether some of the lowest doses of natural estrogens currently prescribed for postmenopausal women result in significant changes in plasma lipids, urinary calcium, urinary free cortisol, or level of androgens. Twenty-four postmenopausal women were studied and the estrogens ingested were either conjugated estrogens (0.3 or 0.6 mg), piperazine estrone sulfate (0.6 or 1.2 mg), or micronized estradiol (1 mg). Plasma lipids were unaltered, with the exception of a decrease in low-density lipoprotein cholesterol in women receiving conjugated estrogens, 0.625 mg, and micronized estradiol. The fasting calcium: creatinine ratio, which was significantly higher than that of premenopausal women, decreased significantly after treatment with all the prescribed doses. There was no correlation between the initial calcium: creatinine ratio and urinary free cortisol or androgen levels. Urinary free cortisol was in the premenopausal range and did not change with treatment; levels of dehydroepiandrosterone sulfate and testosterone were significantly lower than premenopausal levels but did not change with treatment. In conclusion, these natural estrogens have no effect on lipids, urinary free cortisol, and androgen levels, but they appear to reduce the urinary loss of calcium in the fasting state.