People with Alzheimer's disease living in a defined community in New York City were identified and assessed on two occasions to determine the number of hours of activities of daily living (ADL) care they received. Nearly half received all care hours from informal sources; however, a quarter received all ADL care hours from formal sources. The mean number of daily ADL hours in the sample was 9.7, of which 4.2 came from formal sources. This reflects the extensive use of Medicaid-based home care services in New York City. As dementia worsened, substitution of formal for informal care was rare, but formal care assumed a greater proportion of total care hours.