Inguinal hernia is a frequent surgical disease during infancy, occurring in 1 to 2% of all mature newborns and rise up to 30% of all premature babies. In 9.5% a contralateral hernia is found after unilateral operation. In our own patients this rate was 5.6%. The development of a contralateral hernia was significantly more often found in boys than in girls. If the hernia occurred during the first two months of life, a contralateral hernia developed later highly significant (p > 0.0001). Within the first two postoperative years the second hernia arose in 84.9%. We recommended to routinely operation for a contralateral hernia in all children younger than two months.