Whenever long-term anticoagulation is prescribed, the risks of such therapy must be evaluated accurately. Whether these risks are influenced by the duration of therapy, the indication for therapy, patient demographics and social habits, or the use of an anticoagulation clinic is controversial. This study examined the occurrence rates of major hemorrhage, minor hemorrhage, and thromboembolic events among an inception cohort of 82 patients receiving long term-warfarin therapy in an anticoagulation clinic. During 199.34 patient-years of observation, there were 4 major hemorrhages (0.0201/patient-year), 31 minor hemorrhages (0.1555/patient-year), and 7 thromboembolic events (0.0351/patient-year). Although each type of event tended to occur during the first 6 months of therapy, this trend was not statistically significant. Failure to demonstrate statistically significant influence of any of the evaluated variables may have been due to the unusually low rate of complications, a finding that may reflect the safety of anticoagulant therapy when managed by a specialized clinic.