For the prevention of later contralateral hernia as well as unnecessary contralateral exploration in pediatric patients with unilateral inguinal hernias, a reasionable indication of contralateral exploration is required. To examine the contralateral positivity, a prospective selective contralateral exploration has been performed by the author from Sept. 1985 to Dec. 1993, at Pediatric Surgical Section of the Department of Surgery, Kangnam St. Mary's Hospital, Catholic University Medical College. Among the total 1200 cases of pediatric inguinal hernias, 580 cases of contralateral side were explored at hernia operations, by the indications as; 1)male with infant onset, 2)female of all age, 3)prematurity, 4)profuse ascites due to cirrhosis, nephrotic syndrome, and ventriculoperitoneal shunt, and 5)remarkable silk sign. Overall positive rate was 71.4%, and positive rates of each indication were 80.7%, 70.4%, 73.1 %, 66.7%, and 72.0%, respectively. Right side hernia showed 67.0%, left side 75.7%, and positive familial history 71.8% of contralateral positivities. In male,getting older revealed lower positive rates and the rate suddenly dropped after 12 years of age. Birth order, mother's age at delivery, postmaturity did not show any significant differences between the rates. Recurrence was seen in 3(0.5%) ipsilateral and 2(0.3%) contralateral, both of which were negative esplorations on previons operations. Overall complication rate was 3.8%, including 1 infection, 14 fluid or blood accumulation, 5 edemas, 3 temporary testicular edemas, 2 persisting fevers, 2 enuresis and one delayed recovery from anesthesia. Among 38 cases with contralateral hernias developed after unilateral surgery by authors(6 cases) or surgeons in other institutions, 14 were males with infant onset, 4 were prematurities and 9 were females. Therefore, 27(71.7%) cases were originaly under the contralateral exploration indications. The primary site of the hermia was right in 25 and left in 13. With above results, the following indications for contralateral exploration could be suggested; 1)under one year of age, both sex, 2)prematurity, 3)remarkable silk sign, 4)in the double checked suspicions among males with infant onset, all age females, ascites, left hernia and familial history. After 12 years of age, exploration is not required. Considering complications, contralateral explorations could be considered only in the following situations ; 1)expert, experienced pediatric surgeon, 2)experienced pediatric anesthesiologist, 3)operations could be done smoothly in an hour, 4)good general condition of the patient.