Ultrasound plays an important role in the diagnostic workup of scrotal diseases. It can differentiate a testicular mass from an extratesticular mass and determine whether the mass is cystic, solid, or complex. Using this information a likely diagnosis can be ascertained. In the acute scrotum, acute epididymitis/epididymo-orchitis can in most cases be distinguished from testicular torsion. Following scrotal trauma, surgery is needed to salvage the testis if there is testicular disruption and ultrasound can help with this diagnostic dilemma. When a large hydrocele is present, ultrasound allows evaluation of the underlying testis and epididymis and it can detect varicoceles, especially in the infertile male. In patients at risk for a testicular tumor (cryptorchid testis, testicular microlithiasis), ultrasound is the best imaging modality for follow-up. CT, MRI, and nuclear medicine scanning may be necessary for further evaluation of scrotal diseases and this will be briefly addressed.