Echocardiographic detection of prosthetic valve-associated strands has previously been reported, but their clinical relevance is unclear. Limited data are available regarding the cause, composition, and natural history of these strands. This report presents the gross and histopathologic findings of an explanted mechanical prosthetic valve shown by transesophageal echocardiography to have several strands. The patient had not experienced prior neurologic symptoms. Potential causes of strand formation in various clinical settings are also discussed.