The article proposes a method to determine the optimal achieved intensity of oral anticoagulant therapy by calculating INR-specific incidence rates of thromboembolic and hemorrhagic events. This method can be applied retrospectively to data from routine patient care or prospectively within clinical trials. The incidence rates are calculated based on the INR at the time of the event and the person-time at each INR value, assuming a linear increase or decrease between consecutive measurements. The method allows for stratification by covariates and multivariate regression analysis to assess the effects of other factors. The optimal achieved intensity can serve as a rational starting point for setting target levels in subsequent clinical trials, providing insights into the variability at different target levels in a care system. The method has been applied in two studies: one to find the optimal intensity of anticoagulation in patients with mechanical heart valves and another to investigate risk factors for bleeding in patients receiving anticoagulant treatment.The article proposes a method to determine the optimal achieved intensity of oral anticoagulant therapy by calculating INR-specific incidence rates of thromboembolic and hemorrhagic events. This method can be applied retrospectively to data from routine patient care or prospectively within clinical trials. The incidence rates are calculated based on the INR at the time of the event and the person-time at each INR value, assuming a linear increase or decrease between consecutive measurements. The method allows for stratification by covariates and multivariate regression analysis to assess the effects of other factors. The optimal achieved intensity can serve as a rational starting point for setting target levels in subsequent clinical trials, providing insights into the variability at different target levels in a care system. The method has been applied in two studies: one to find the optimal intensity of anticoagulation in patients with mechanical heart valves and another to investigate risk factors for bleeding in patients receiving anticoagulant treatment.