Measuring the performance of electronic health records (EHR) is an important, yet un-resolved challenge. Various measurements have addressed different aspects of EHR success, yet a holistic, comprehensive measurement tool needs to be developed to capture the potential EHR success variables completely. A self-administered questionnaire survey instrument was developed based on the theoretical framework of the DeLone and McLean Information Systems Success Model. It measures nigh variables of EHR success: system quality, information quality, service quality, training, self efficacy, intention to use, use, user satisfaction and net benefits. The instrument was used to measure the performance of aged care EHR systems in three aged care organizations. The results suggest that the instrument was reliable.