Antagonistic peptides of GnRH having improved water solubility are disclosed.These peptides are capable of suppressing serum testosterone levels in vivo tochemical castration levels of <；=0.5 ng/ml. Stable, filter sterilizable, non-gelling solutions containing the GnRH antagonists at least at levels typicallyused in sustained release formulations also are disclosed, as is a method ofincreasing the solubility of GnRH antagonist in a polymer containing dispersedphase, which method comprises addition of an acid to the dispersed phase.
