The purpose of this study was to quantify morbidity burdens of children with intellectual disability (ID) and to examine its association with total medical utilization and expenditure on a national basis in Taiwan. People under 18 years of age that had been continuously enrolled in the National Health Insurance (NHI) between year 2008 and 2010 were selected from one million randomly-sampled NHI beneficiaries. The Johns Hopkins Adjusted Clinical Group (ACG) System was applied to evaluate an individual's morbidity burden using 2008-2010 claims data, including age, sex, diagnosis, pharmacy, ambulatory, and inpatient utilization and expenditure (in New Taiwan Dollars, NTDs). The ID prevalence rate was 0.69% for people aged under 18. People with ID could be assigned to 20 mutually exclusive ACGs and to five simplified morbidity categories: healthy (0.1%), low (1.5%), moderate (31.9%), high (44.0%), and very high (22.4%). People with ID had more per capita visits (108.4 vs. 51.5, p less than 0.001), hospital admission (27.7% vs. 13.1%, p less than 0.001), pharmacy (NTD 21,069 vs. 4983, p less than 0.001) and total expenditure (NTD 144,962 vs. 29,764, p less than 0.001) than those without ID over 3 years. Those who assigned to the high-morbid categories cost more in ambulatory and inpatient services than those with low to moderate morbidities. In conclusion, the morbidity burdens of people with ID can be quantified by the ACG System based on readily available data. Regularly evaluating morbidity burdens and medical utilization has particular relevance for planning high-quality and efficient care. People's disabilities and comorbid illnesses shall be treated by integrated multidisciplinary teams. (Contains 2 figures and 4 tables.)