Between July 1986 and March 2006, 102 patients underwent an operation for acute scrotum. Median age was 12.0 years old (range 0-51). Post-operative diagnosis revealed 50 cases (49%) of spermatic cord torsion, 29 cases (28%) of epididymal appendix torsion, and 13 cases (13%) of acute epididymitis. Spermatic cord torsion was most frequent in the age between 0 and 5, and 11 and 20, while epididymal appendix torsion was most frequent between 6 and 10. Moreover, acute epididymitis was most frequently seen in the age over 20. There were no apparent differences in the clinical symptoms such as scrotal pain, scrotal swelling, and abdominal pain. In the physical examinations, pyuria was the only finding to indicate acute epididymitis. In case of spermatic cord torsion, 'golden time' is defined as the time from onset to operation when testicular function can be expected for preservation. In this study golden time was defined as 8 hours because the testes was preserved in all 23 patients receiving the operation within 8 hours, but in only 10 (37%) out of 27 patients receiving the operation after 8 hours. Moreover, the operation within 24 hours saved the testes in approximately 90% of the patients. In patients with acute scrotum, emergency operation should be performed as speedily as possible for preservation of testicular function.