The share of Medicaid beneficiaries with intellectual/developmental disability (I/DD) in five states ranged from 2.3% of the state’s total Medicaid members in New York to 4.2% in South Carolina. Across the five states (Delaware, Iowa, Massachusetts, New York, and South Carolina), over 300,000 Medicaid members had I/DD. The most frequent diagnoses were unspecified intellectual disability, autism or pervasive developmental disorder (PDD), and cerebral palsy. The rate of intellectual disability ranged from 0.86% in New York to 2.5% in South Carolina; the rate of moderate to profound intellectual disability ranged from 0 . . .