Prostaglandin metabolism and the clinical effect of epoprostenol (prostacyclin, PGI2) infusions were studied in thirteen patients with Raynaud's disease. Epoprostenol was infused at 5 ng/kg/min for six hours daily for two consecutive five day periods, separated by a two day interval. No beneficial effects either during or after infusion could be detected in terms of frequency of severity of attacks or on skin temperature measurement. Raynaud's patients had significantly lower serum thromboxane B2 levels than normal controls though plasma levels of thromboxane B2, 6-oxo-PGF1 and the bicyclic metabolite of PGE2 did not differ between the two groups. Platelets from Raynaud's patients had a significantly lower conversion rate of arachidonic acid into thromboxane B2 and HHT and a significantly higher rate of HETE production than platelets from controls.