Experience with long-term anticoagulant therapy during the past seven years has been summarized. This report is based on the records of 227 individuals treated as private or outpatient clinic patients for from four weeks to seven years. Where adequate laboratory facilities are available outpatient long-term therapy may be satisfactorily controlled by physicians familiar with the use of anticoagulant drugs. Their correct use will lessen the incidence of thromboembolic episodes in patients who have previously suffered from such complications.