New onset of pain, swelling, and/or tenderness of intrascrotal contents is referred to as acute scrotum. Urgent surgery is indicated unless spermatic torsion is excluded because spermatic torsion is a urological emergency and requires urgent detorsion to salvage the affected testis . While the usefulness of radionuclide imaging or magnetic resonance imaging (MRI) as diagnostic modalities for acute scrotum has been reported in several articles, ultrasound is mostly indicated recently. Evaluation of blood flow in the affected testis by color Doppler ultrasonography as well as gray-scale mode is quite important in the diagnosis of testicular torsion. In our experience, one-third of the patients with acute scrotum were successfully treated with conservative management, avoiding emergent surgery, because of normal blood flow in the affected testis demonstrated by color Doppler ultrasonography. However, it was reported that blood flow in the affected testis was identified in 20-30% of patients with torsion of the spermatic cord. Therefore, detection of blood flow in the affected testis is not always a definitive finding in the diagnosis of torsion of the spermatic cord. Physical examination or the whirl pool sign on color Doppler ultrasound is also important so as not to miss torsion of the spermatic cord. Urgent surgery should not be avoided unless the diagnosis of torsion of the spermatic cord is completely ruled out. Since ultrasound is an operator-dependent modality, a skillful operator in the emergency room would be warranted to make a better management strategy for patients with acute scrotum.