A positive correlation between the expression of estrogen sulphotransferase (EC 2.8: 2.4) and the estrogen receptor (ER) in human breast cancer tissues was previously demonstrated. We have now established that a similar correlation exists between the expression of hydroxysteroid sulphotransferase (EC 2.8: 2.2) and ER in such tissues. Enzyme activity was present in 93% of the ER + tumor cytosols (mean 59 +/- 44 (SD) pmol dehydroepiandrosterone sulphate formed per mg protein per 2 h (n = 42). Activity was detected in 68% of ER - tumors and this was significantly lower (mean 21 +/- 26 (SD) (n = 19), P less than 0.001) than the former group. Metabolism of estradiol-17 beta (E2) and the adrenal-derived estrogen 5-androstene-3 beta, 17 beta-diol (ADIOL), which is a substrate for hydroxysteroid sulphotransferase but not estrogen sulphotransferase, was studied in four ER + human mammary cancer cell lines (MCF-7, T47-D, MDA-MB-361 and ZR-75-1) and four ER-human mammary cell lines (BT-20, MDA-MB-231, MDA-MB-330 and HBL-100), employing steroid concentrations of 1 nM. At this concentration, formation of ester sulphates was a major route of metabolism in the ER + cell lines; E2 yielding a mean of 6.5 pmol estrogen monosulphates/mg DNA in 16 h and ADIOL yielding a mean of 9.4 pmol C19-5-ene steroid monosulphates/mg DNA in 16 h. In three of the four ER - cell lines, formation of sulphates from E2 occurred at an eight-fold lower rate (mean 0.8 pmol estrogen sulphates/mg DNA in 16 h), whereas MDA-MB-330 cells did not form estrogen sulphates. Only one of the four ER- cell lines (BT-20) sulphurylated ADIOL and this was at a 12-fold lower rate compared to the mean value for the ER + cel lines. Oxidation of E2 and ADIOL occurred in all cell lines and was generally the major route of metabolism in the ER - cells. A significant correlation between formation of estrone and dehydroepiandrosterone occurred for all cell lines (r = 0.98, P less than 0.001) indicating that the same 17 beta-hydroxysteroid dehydrogenase was probably involved. Since ADIOL is estrogenic in a number of systems at the concentration found in the blood of Western women (approximately 2 nM), the coordinated expression of hydroxysteroid sulphotransferase, estrogen sulphotransferase, and ER, supports the concept of a functional relationship between estrogen action via ER and sulphurylation reactions.