Though the application of the hospital morbidity is very limited due mainly to the biasing aspect of the data, some important uses can be made by formulating a norm of hospital disease pattern in investigating the deviation of a hospital's patients morbidity or in time-series analysis of such morbidity. A most feasible way of establishing a representative norm of inpatients morbidity from the hospital statistics is to use the modal rank distribution of disease categories according to the magnitude of its relative proportion. The level of classification recommendable for this purpose is the three-digits code disease categories listed in International Classification of Disease (the latest edition), World Health Organization. The distribution of disease in the ordered ranks demonstrated a high degree of consistency in both intra and inter hospital comparison with rank correlation reaching the level of as high as 0.99.