Background and Purpose: In this prospective study, we compared the clinical efficacy between transinguinal laparoscopic exploration and conservative follow-up in detecting a contralateral metachronous inguinal hernia (CMIH). Methods: Between May 1999 and April 2004, 214 children with a primary unilateral inguinal hernia were randomly assigned to 2 groups in a 4:1 ratio. In group A were 172 children who had a simple herniotomy and were given conservative follow-up after the primary unilateral herniotomy. In group B, 42 children underwent a unilateral herniotomy and transinguinal laparoscopy in the contralateral groin area. The contralateral groin was examined with an 8-Fr. 30˚ endoscope through the hernia sac. When a contralateral patent processus vaginalis (PPV) was diagnosed, it was explored and treated with a regular herniotomy. Results: Six patients in group A who were lost to follow-up were excluded. In group A, 4 (1.9%) patients had recurrence of the inguinal hernia, and 15 (9.0%) had CMIH. In group B, 8 (19%) patients had PPV, all of which were confirmed by surgical exploration. Four (11.7%) patients with negative results of the laparoscopy had CMIH. Conclusions: Transinguinal laparoscopy was unable to predict the occurrence of a contralateral metachronous inguinal hernia.