We have previously shown that adrenaline infusion induces an almost twofold increase in systemic thromboxane synthesis, measured as urinary 11-dehydrothromboxane B2. The purpose of the present study was to investigate whether high levels of adrenaline, found e.g. in heavy physical exercise and myocardial infarction are involved in the regulation of prostacyclin synthesis. To this end the effect of adrenaline infusion (0.1 microgram/kg/min for 45 min and thereafter 0.2 microgram/kg/min for 15 min) on prostacyclin synthesis in healthy male volunteers was investigated. Adrenaline infusion produced an over twofold increase in systemic prostacyclin synthesis, measured as urinary 2,3-dinor-6-keto-prostaglandin F1 alpha. Our study demonstrates that high circulating levels of adrenaline are associated with increased formation of prostacyclin.