Two consecutive male infants born to healthy parents died shortly after birth. Both had severe anomalies of the urinary tract. The first had bilateral agenesis of the kidneys, and the second had agenesis of one kidney and total dysplasia of the opposite. The question of the chance of recurrence in a subsequent pregnancy arose. With this in mind, reported instances of unilateral renal agenesis, bilateral renal agenesis, and total renal dysplasia occurring in families were reviewed. From the data currently available, it is not possible to predict the relative risk of recurrence of these anomalies. The data suggest the possibility of an autosomal-recessive pattern or a possible environmental or teratogenic factor.