A 66-year-old man underwent surgery to remove an incidentally discovered non-tender intrascrotal mass. Ultrasonography revealed an irregular-margined, heterogeneous mass-like lesion in the epididymal tail. The mass was relatively well circumscribed but unencapsulated, irregular and firm; it consisted of expansile, increased smooth muscle fascicles originating from the epididymal muscular coat. Its cellular growth pattern lacked the cohesive, well-circumscribed proliferation pattern typical of a leiomyoma. A diagnosis of smooth muscle hyperplasia of the epididymis was made. Although ultrasonography is the imaging modality of choice for evaluating suspected intrascrotal masses, there are times when it cannot reliably identify the character of the masses and distinguish malignant from benign lesions. Ill-defined, solid extratesticular masses, that are ultrasonographically ambiguous, should be excised and confirmed histopathologically and smooth muscle hyperplasia of the epididymis should be included in the differential diagnosis of solid extratesticular masses.