SUMMARY Urinary excretion of prostaglandin E 2 (PGE 2 ) and F^ (PGF^), plasma concentrations of renin, aldosterone, norepinephrine (NE) and epinephrine (E) were determined during pregnancy, 5 days, 3, and 6 months after delivery in preeciampsia, normotensive pregnant, and nonpregnant control subjects. The PGE 2 was higher in normotensive pregnant control subjects than in nonpregnant subjects. In preeciampsia, PGE, was reduced to nonpregnant level. PGF^ was the same in preeciampsia and in normotensive pregnancy, but elevated when compared to the normotensive nonpregnant control group. Plasma concentrations of renin and aldosterone were increased during pregnancy, but considerably less in preeciampsia than during normotensive pregnancy. NE and E were the same as in nonpregnant subjects during both hypertensive and normotensive pregnancy. All parameters were normal 3 months after delivery. There were no correlations between PGE 2 , PGF^, plasma concentrations of renin, aldosterone, NE, or E and blood pressure level in third trimester either in preeciampsia or in normotensive pregnancy. PGE, was positively correlated to plasma concentrations of renin. It is suggested that the lack of renal PGE 2 in preeciampsia might be responsible for the decrease in renal blood flow and sodium excretion. It is hypothesized that preeciampsia is a state of prostaglandin deficiency. The changes in the renin-aldosterone system may be secondary to changes in prostaglandin concentration both in preeciampsia and normotensive pregnancy. Received March 16, 1982, revision accepted August 12, 1982 with simultaneous evaluation of urinary prostaglandin excretion, the renin-aldosterone system, and sympathetic adrenergic activity in preeciampsia and normotensive pregnancy both before and after delivery.In the present study we measured urinary excretion of prostaglandin E 2 (PGE 2 ), prostaglandin F 2a (PGF 2 J, plasma renin concentration, plasma aldosterone concentration, plasma norepinephrine (NE) and plasma epinephrine (E) in patients with preeciampsia and in normotensive pregnant and nonpregnant control subjects. The pregnant groups were studied during pregnancy and 5 days, 3, and 6 months after delivery. To reveal possible pressor or depressor mechanisms in preeciampsia, it was our purpose to study changes in these parameters, correlations between these parameters and blood pressure, and relationships between urinary prostaglandins, the renin-aldosterone system, and the sympathetic nervous activity.