Controversy continues whether exploration of the contralateral, asymptomatic side should routinely be performed since Rothenberg and Barnett stated in 1955 that a contralateral hernia is present in three out of four children presenting with a symptomatic unilateral inguinal hernia (IH). In our institution, hernia operations are performed on the symptomatic side only, the exception being male infants under 1 year of age with a left-sided IH. To verify our concept and to evaluate the frequency of contralateral hernial development, the medical records of all infants under 1 year of age operated upon between 1984 and 1988 were reviewed and the children followed through December 1996. Included in the study were 882 infants, 616 boys (70%) and 266 girls (30%); 148 (17%) were born prematurely. Seventy percent were operated upon before the end of the 3rd month of life. In 761 infants clinical signs of a unilateral hernia were present, and in 121 symptomatic hernias were found on both sides; 665 infants were operated upon unilaterally. A second operation on the opposite side was necessary in 38 cases (5.7%). The highest incidence of contralateral hernial development was found in premature boys (11.5%). We conclude that even in infants below 1 year of age, IH is usually a unilateral disease and does not require routine exploration of the asymptomatic side.