The role of prostaglandins in the control of aldosterone production was studied in isolated rat glomerulosa cells. Exogenous prostaglandin E2 in concentrations above 10(-9) mol/l increased the production rate of aldosterone; this effect was attenuated by the competitive antagonist, 7-oxa-13-prostynoic acid. Prostaglandin F2 alpha (10(-9)--10(-5) mol/l) failed to influence the production rate of aldosterone. The aldosterone-stimulating effect of the prostaglandin precursor, arachidonic acid (5 x 10(-4) mol/l), could not be blocked by inhibitors of prostaglandin synthesis. Basal production rate of aldosterone was not significantly influenced by non-steroidal anti-inflammatory drugs. Glomerulosa cells were stimulated by angiotensin II; this effect was not potentiated by arachidonic acid and was reduced only slightly by indomethacin. The cells were also stimulated by corticotrophin and potassium ions. The effect of these substances was not potentiated by arachidonic acid and was not inhibited by non-steroidal anti-inflammatory drugs. These results do not confirm the presumption that intra-adrenal prostaglandins play an essential role in the control of aldosterone secretion. Some effects of arachidonic acid and its antagonist, eicosatetraynoic acid, on aldosterone production are considered to be independent of changes in prostaglandin synthesis.