Background: Disease pattern is an important informational tool used by policymakers in setting priorities, strategies and allocating budgets to address the precursors or causes of health problems.
Objective: To analyze the common diseases in the adult population using in-patient information from the three health insurance coverage schemes in the fiscal year 2010.
Material and Method: The authors analyzed the data on in-patients with 23 major disease groups as per ICD-10 coding. The data were analyzed to obtain the number of patients, number of admissions, number of hospital mortalities, mortality rates and length of hospital stays.
Results: The total number of adult in-patients was 3,876,792 presenting for admission 4,863,935 times. Infectious and parasitic diseases were the most common causes of admission. Diseases of the circulatory system resulted in the highest number of mortality rate (8.72%). Intracerebral hemorrhage, neoplasm, septicemia, liver failure, coronary heart disease, HIV/AIDS, status epilepticus, pneumonia, accidents and acute renal failure were the top ten diseases with a high mortality rate.
Conclusion: The review indicated communicable diseases are the most common disease group although non-communicable diseases were also important because of their high mortality rate.

Keywords: Disease pattern, Thai adult population