In rats, the catabolism normally induced by chronic dihydrotachysterol (DHT) intoxication is counteracted (in approximately decreasing order of activity) by: norbolethone, ethylestrenol, CS-1 and pregnenolone-16α-carbonitrile (PCN). Spironolactone was previously shown to antagonize DHT in acute experiments. However in the chronic experiments reported here, it is inactive in this respect and even abolishes the high anti-DHT of norbolethone and ethylestrenol. Several possible mechanisms are discussed which might explain these antagonisms, for example: (1) Spironolactone may act by accelerating the enzymatic degradation of the protective anabolic steroids. (2) The 2 types of steroids may compete with each other for receptor sites. (3) Spironolactone and the anabolics may exert opposing actions on DHT metabolism.