With the idea of clearing out several variables individually found associated with a greater incidence of congenital pyloric stenosis in the same group of children, 298 clinical histories in infants complaining of this deviation were reviewed. Information was obtained as to sex, birth number, blood group and the month these children with stenosis were born. The distribution of frequencies in each one of these variables was compared to that in 309 children surgically operated from peritonitis. The results showed a greater incidence of congenital pyloric stenosis in males than in females; also, the disease appeared more frequently in first-borns. Patients with type A blood group were less prone to present the anomaly. The birth month showed no statistical difference. The findings stress the importance shown by the genetic component of this disease.