Five brief case reports are given of men who had incestuous sexual relationships with their daughters. Intelligent, middle-class men with fair jobs, they had character disorders with paranoid features and well-organized intellectual defenses and rationalizations. All had regressive longings and had failed to achieve an adult masculine identity. The data suggest an ego or superego defect, or both, in the man with contributions by the wife and daughter, but no specific causal factors were found.