Results: The result of validation study from 196 patients shows that the expert system is fairly better than Siriraj's and Nguyen Ba Thang's clinical scale: sensitivity of the expert system for diagnosing cerebral haemorrhage in comparison with Siriraj's and Nguyen Ba Thang's clinical scale is 99.05% in comparison with 75.61% and 98.04%; sensitivity of the expert system for diagnosing cerebral infarction is 92.54% in comparison with 90.79% and 83.82%; overall accuracy of diagnosis is 96.51% in comparison with 82.91% and 92.35%; rate of vague diagnosis is 12.25% in comparison with 19.39% and 13.27%.