To determine whether intra-abdominal pressure may have a role in the process of testicular descent in man, we reviewed retrospectively the records of all male infants who presented during a 10-year period with severe abdominal wall defects, such as gastroschisis (28), omphalocele (29) and umbilical hernia (53), and calculated the incidence of cryptorchidism in these patients. The incidence of cryptorchidism at birth and at 1 year after birth was 18 and 15 per cent, respectively, in patients with gastroschisis, 52 and 33 per cent, respectively, in those with omphalocele, and 6 and 6 per cent, respectively, in those with umbilical hernia. For all 3 disorders the incidence of cryptorchidism was higher than in documented historical controls. From these data we conclude that in male infants there is an association between these 3 abdominal wall defects and cryptorchidism. The demonstration that intra-abdominal pressure is lowered significantly by these abdominal wall defects would suggest a possible role for intra-abdominal pressure in the process of testicular descent in man.