Abstract: Eighty-four patients with mitral stenosis and cerebral embolism have been followed up for 20 years. Half of the series (those treated in the early years) had no anticoagulant treatment and half were given long-term warfarin therapy. Mortality rate and causes of death have been reviewed, and comparison of survival times of treated and untreated groups by life-table analysis bears out the immediate need for anticoagulants when a diagnosis of systemic embolism is established. It is wise to continue the treatment for six months but it may be reasonable to discontinue it after one year with patients who can be assured of regular review.