In order to clarify the role of thrombolytic therapy for the treatment of left sided prosthetic valve thrombosis, a composite analysis of 158 cases reported in the English literature was undertaken. Complete success of therapy was achieved in 68.4% of patients, and the results were better in patients with aortic compared to mitral valve prostheses (p < 0.01), in those presenting in lower NYHA class (p < 0.01), and with acute rather than chronic symptoms (p < 0.05). A successful outcome was seen more frequently with tilting disc than bileaflet valves (p < 0.001). Overall mortality during therapy was 7%. Cerebral embolic events were observed in 9.5% of patients, and irreversible neurological injury occurred in 4.4%. The rethrombosis rate was 17% and the incidence of late death was 6.3%. Thrombolysis may be a useful therapeutic alternative for left sided prosthetic valve thrombosis in patients with a perceived contraindication to surgery. The risks of systemic clot embolization along with incomplete resolution of valve leaflet motion or rethrombosis limits any recommendation for more widespread use.