✓ A rare case of peripheral-nerve compression in the upper arm caused by a spontaneous venous aneurysm is reported. The apparent dysfunction of the median nerve led to various vain surgical explorations of the nerve at different levels. The real localization of nerve entrapment was identified by a thorough clinical examination, and sonography yielded a correct diagnosis. Surgical resection of the venous aneurysm resulted in complete relief of pain. To the authors' knowledge, this is the first report of a spontaneous venous malformation in the upper arm causing focal neuropathy.