This study aims to analyze the ambulatory visit frequency and medical expenditures of the general elderly population versus the elderly with intellectual disabilities in Taiwan, while examining the effects of age, gender, urbanization and copayment status on ambulatory utilization. A cross-sectional study was conducted to analyze data from 103,183 national health insurance claimants aged 65 or older. A total of 1469 had a principal diagnosis of mental retardation (intellectual disability) and claimed medical outpatient services in 2007. The average number of ambulatory visits was 30.1 ± 23.1, which is much higher than in the United States and other developed countries, and the mean annual visits of the elderly with intellectual disabilities was significantly higher than the general population in Taiwan (35.2 ± 28.7 vs. 30.0 ± 23.1). Age and copayment status affected outpatient visit frequency. The mean medical expenditure per visit and the mean annual outpatient cost were 1146.5 ± 4497.7 NT$ and 34,533.7 ± 115,891.7 NT$, respectively. Male beneficiaries tended to have higher average annual medical expenses and mean medical expenses per visit than female beneficiaries. The three most frequent principal diagnoses at ambulatory visits were circulatory system diseases, musculoskeletal system and connective tissue diseases and digestive system diseases. We conclude that the elderly with intellectual disabilities had higher demand than the general population for healthcare services, and the NHI program lowers the barrier to care for populations with special needs.