The role of prostaglandin (PG) system in preeclampsia (pre-E) was investigated. Urinary excretion of PGE2,6-keto PGF1 alpha,2,3 dinor 6-keto PGF1 alpha, TxB2 and 2,3-dinor-TxB2 and kallikrein were determined in 10 normotensive pregnant women and 14 with pre-E. 6-keto PGF1 alpha and 2,3-dinor 6-keto PGF1 alpha (the main renal and extrarenal metabolites of vasodilator PGI2) and PGE2 excretion was lower in pre-E. TxB2 metabolites in urine were similar in the two groups of women. Our data are consistent with the hypothesis of an imbalance between vasodilator and vasoconstrictor PGs in pre-E.