Objectives:The purposes of this study were to develop an online computer-assisted instruction method and assess its efficiency in terms of propriety, feasibility, accuracy and utility standards. Method:The sample consisted of third-year medical students and critical care nurses, who volunteered to join the study. Research tools included online activities and student assessments, open-ended questionnaires and students' record profiles. Data was analysed using the percentage, mean, standard deviation, correlation coefficient and t-test.Results: A total of 83 out of 116 third-year medical students (71.55%) and 35 out of 56 critical care nurses (62.50%) registered through the website, and completed the learning courseware. Results of the system efficiency assessment through the tests and open-ended questionnaires showed that it was highly appropriate for use in communicating for learning; it was also found that the system was highly feasible in stimulating learners to continuously plan for self-directed learning and for system accuracy. It appeared that the system had objectivity, construct validity, concurrent validity, and internal reliability; and for system utility, it was found that learners gained high learning achievement and growth scores. Online record profiles revealed that 63 medical students and 35 nurses appreciated the significance of the developed online learning system as fair to full. Conclusion:The online computer-assisted instruction method was highly efficient. Through selfdirected learning, the students were stimulated to apply problem-solving strategies, individual help seeking strategies, and self-regulation, as well as develop critical thinking with discretion for selfassessment and continue learning with a sense of self-actualization and self-esteem.