The effects of zinc deficiency on the binding of PGF2 alpha to ovarian membranes and of PGE1 to intact platelets prepared from pregnant rats were examined. On d 21 of gestation, rats fed low zinc (less than 1 ppm) diets throughout pregnancy had prostaglandin receptor characteristics significantly different from those of rats fed control diets (100 ppm zinc). The number of binding sites for PGF2 alpha was higher in the ovarian membranes prepared from deficient rats than in those from controls, whereas the affinity was not affected. In washed platelets from zinc-deficient rats there were fewer PGE1 binding sites but greater affinity for PGE1 than in platelets from controls. These results demonstrate that zinc status affects prostaglandin binding to membranes. The effects are not uniform with regard to different tissues and prostaglandin receptors but suggest an effect of zinc status on plasma membranes.