The literature indicates that beta-endorphin can be found in the mononuclear cells of peripheral blood. In the present experiments the endorphin content of granulocytes was studied, compared to lymphocytes as reference cells. Granulocytes as well, as lymphocytes contain endorphin. The granulocytes' endorphin content is much higher. Both lymphocytes and granulocytes are also able to take up endorphin from the milieu.