The case histories of a family demonstrating familial maldevelopment of the os pubis without associated developmental anomalies are evaluated. The father and each of his three sons demonstrated variations in development and ossification of the pubic bones which simulated diastasis of the symphysis pubis. True diastasis is generally associated with developmental abnormalities of the genitourinary tract, including epispadias and bladder exstrophy. Maldevelopment and'or ossification abnormalities are also seen in cases of cleido-cranial dysostosis and sporadically as isolated defects.