Inositol phospholipid breakdown, from a [3H]inositol-labelled pool, induced by a variety of contractile agents was monitored in uterine smooth muscle slices pretreated with estradiol-17 beta or estradiol-17 beta and progesterone by measuring the accumulation of [3H]inositol phosphates. Agonist potencies for stimulating [3H]IP accumulation were not affected by hormone treatment but the maximum responses were dependent upon hormonal state. Maximum responses to carbachol, norepinephrine, prostaglandin F2 alpha were increased in progesterone-dominated tissues but maximum responses to oxytocin were unaffected. Inhibition of agonist-induced responses by competitive receptor antagonists confirmed the receptor specificity of carbachol-, norepinephrine- and oxytocin-mediated responses. Partial membrane depolarization (25 mM K+) did not affect agonist-induced maximal responses in either estrogen- or progesterone-dominated tissue. These data suggest that gonadal steroid hormones affect agonist-dependent intracellular calcium mobilization processes.