Histamine receptors on the surface of E. histolytica could be demonstrated by histochemical method using three isolates of the protozoa grown and maintained in modified Boeck and Drbohlav's medium. Prior treatment of E. histolytica with cimetidine a H2 blocker, blocked the histamine uptake. Similar treatment with mepyramine maleate, a H1 blocker, did not prevent histamine uptake by the protozoa. It is postulated that E. histolytica has H2 receptors on its surface.