Thyrotoxic artrial fibrillation is well known and occurs in 10-30% of all patients with thyrotoxicosis. The risk of systemic embolism has been found to be 10-40% in patients with thyrotoxic atrial fibrillation. We present a case of 53 year-old man, a healthy and active athlete, with atrial fibrillation and thyrotoxicosis. He was treated with a beta-blocking agent (sotalol) and sent home. Seven days later, he suffered systemic arterial emboli, one in the right arm and one in the left leg. After embolectomy the patient started anticoagulation and no further complications occurred. Previous studies are discussed, and the following conclusions made. When taken together the data suggest that the rate of embolism in patients with thyrotoxic atrial fibrillation exceeds that of non-thyrotoxic atrial fibrillation unassociated with rheumatic heart disease. The majority of clinically evident embolic events that occur in patients with thyrotoxic atrial fibrillation involve the central nervous system. The rate of embolic events appears to be greatest early in the course of thyrotoxic atrial fibrillation, but may persist for some weeks after conversion and may be particularly high in patients with associated heart failure. It is suggested that anticoagulation therapy should be considered in these patients.