It is well known that in haemodialysis patients suffering from oligoanuria, extracellular hypervolaemia develops and this hypervolaemia is the main reason for hypertension occurring in some of the patients. The absence of vasorelaxation during hypervolaemia may be secondary to an increased activity of vasoconstrictor systems and/or a decreased formation of vasodilator agents like prostaglandin E-2(PGE(2)) and prostaglandin I-2(PGI(2)). In the present study, arterial PGE, and leukotriene C-4(LTC4)-like activities and the effect of fluid removal on these arachidonic acid metabolites during haemodialysis were measured in normotensive and hypertensive patients. Plasma PGE(2) and LTC4-like activities were significantly different between hypertensive and normotensive patients. PGE(2)/LTC4 ratio did not change in normotensive patients while it was increased in hypertensive patients after haemodialysis. These results indicate that haemodialysis alters the synthesis of arachidonic acid metabolites especially in hypertensive patients.