In this article the author first presents three clear-cut examples to demonstrate how delusional ideas of contamination function as defenses against sexual thoughts. The first case is a paranoid man who showed strong homosexual tendencies which he repudiated and who thought that he was infected, drugged and castrated. The second case is another paranoid man who heard voices accusing him of homosexual practices and who suffered from the delusion that his wife was poisoning him. He was totally impotent. The third case was a man who like the two preceding had had no sexual relations. After twenty-three years of dental practice he suffered from influenza after which a young