The diagnosis of Hirschsprung's disease is at times difficult, particularly in the young patient. Since 1972 we have used rectal suction biopsy as a screening technique in neonates and infants with failure to pass meconium or evidence of obstruction. In addition, it is used to confirm the diagnosis of Hirschsprung's disease when suspected by barium enema study. This technique has been used in 444 patients, 302 of whom were less than one year of age. No anesthesia is necessary, and there have been no associated complications. Only one patient early in the study had an initial misdiagnosis. There have been no false-positive or false-negative specimens since this initial problem, and no patients have undergone inappropriate pull-through procedures for suspected Hirschsprung's disease. It is recommended that all neonates who do not pass meconium in the first 48 hours of life undergo rectal suction biopsy to establish the diagnosis of congenital megacolon.