A fraction with bradykinin potentinating activity was chemically isolated from the venom of the Egyptian scorpion Buthus occitanus. The pharamacological activity of the fraction (BPF) was bioassayed by the ability to potentiate added BK on the isolated guinea pig ileum as well as its inhibitory activity on ACE. The mode of action of this fraction on gonads of immature female guinea pigs was measured. The fraction was i.p. injected 1 ug/g body weight for five times in animalsat successive time intervals of 7 days each. Total body, ovaries, and uterine tissue weights were significantly increased as well as uterine total protein, RNA and cyclic nucleotides contents. Concomitantly, PGE2 level showed a significant elevation in both uterine and ovarian tissues. The uterine tissue homogenates in vitro showed an enhancing effect in response to the added fraction (1 ug/ml) and BK (i ug/ml) for PG biosynthesis from radiolabelled precursor 14 C-linoleic acid into its labelled metabolites AA, PGD2, TxB2, PGE1, PGF1 a and 6-keyo PGF1a.This enhancement effect was abolished in the presence of BK inhibitor , but the labelled PGF2a was still high. The results clearly indicate that the increase of PGs resulting from both in vivo & in vitro experiment may contribute to the inhibition of ACE and potentiation of exogenous and endognous BK.