Clinical experiences of 833 hydrocele children presented at Hanyang University Hospital, of whom 456 children were operated by one pediatric surgeon from September 1979 to December 1993, were analyzed. Eight hundred and twenty three children were boys(right 476, left 279, bjJateral 49, and unknown 19), and 10 weregirls(8 right and 2 left). Operation was performed on 446 boys and all girls. Of boys diagnosed before the age of 6 months, 15.6% was operated and 68. 7% of those after 6 months of age was operated. Among the boys operated after 2 years old, 16.5% had had hydrocele before 6 months of age, 20.4% before 1 year old and 34.6% before 2 years old. On the other hand, 28.8% of boys diagnosed after 2 years of age did not undergo hydrocelectomy. Sixteen children with hydroceles had contralateral hernias at the same time. After repair of unilateral hydroceles, contralateral hydroceles developed in 7 and hernias in 3 children. After disappearance of unilateral hydroceles, it reappeared at the same site in 4 and contralateral hydroceles or hernias developed in 2 children each. Hydroceles converted to hernias in 6 children before treatment. Hydroceles developed after ventriculo-peritoneal shunt in 5 children. The pathophysiology of hydrocele and inguinal hernia seems to be the same because of the similar distribution of onset age between them but hydrocele has various clinical courses. The results that 34.6% of boys operated after 2 years old had had hydrocele before 2 years of age and 28.8% of boys diagnosed after 2 years old did not undergo hydrocelectomy could not imply the proper age when hydrocelectomy could be performed. But operative repair of hydroceles after the age of 6 months seems to be recommendagle.