PURPOSE: We determined the rate of an occult contralateral inguinal hernia by conducting only a physical examination for the unilateral inguinal hernia patients who visited our hospital. METHODS: One hundred thirty nine patients were prospectively evaluated between September 2009 and October 2010. We divided the patients into 3 groups according to a physical examination of the contralateral inguinal area: Group A (no abnormality), Group B (suspicious) and Group C (definite). We defined Group B and Group C as possible occult bilateral hernia. In Group B, selective diagnostic laparoscopy was performed after the totally extraperitoneal herniorrhaphy was finishedover. We analyzed the rate of detecting a contralateral hernia, the positive predictive value and the accordance rate. RESULTS: Of the 139 patients, the number of patients in Group A, B and C were 113 cases, 4 cases and 22 cases, respectively. The age of the patients ranged from 18~86 years (mean age: 57.1), with a male to female ratio was 7:1. Twenty-six patients (18.7%) had possible occult bilateral hernia. For the left inguinal hernia patients, the incidence of contralateral hernia was 18.2% (12/66). For the right inguinal hernia patients, this was 19.2% (14/73). The detection rate of contralateral hernia by physical examination was 14.1% (19/135) and the positive predictive value was 86.4% (19/22). The accordance rate of simultaneous bilateral hernia was 57.9% for the direct hernia patients and it was 26.3% for the indirect patients. There was no recurrence or metachronous contralateral inguinal hernia occurrence. CONCLUSION: We can discover occult contralateral inguinal hernia by conducting a careful physical examination of the contralateral inguinal area. Conducting a proper physical examination is very important for detecting inguinal hernia.