The overall goal of this supplement is to build on a unique sample of older adults with ASD (who are members of the Autism Speaks-funded Quality of Life study) to design pilot-level research on aging and dementia in individuals with ASD. Preliminary findings from this research team indicate that, following an increase during adolescence and young adulthood, adults with ASD evidence a decline in functional skills during midlife and beyond. This pattern of decline is in sharp contrast to the upward slope and linear nature of the trajectory of functional skills during a similar period in adults with Down syndrome, where skills are maintained more successfully. Many explanations are possible for this downward trajectory of functional skills among adults with ASD in midlife and beyond, and one of these is dementia. The supplement will focus on two Specific Aims: Aim 1: To conduct secondary analysis (using both qualitative and quantitative approaches) of existing data to identify patterns and predictors of decline in behavioral and functional abilities in midlife and older adults with ASD. The aim will focus on domains have previously been associated with dementia in the larger (non-ASD, non-ID) population. This aim also will identify individuals for pilot testing the dementia assessment screening protocol for Aim 2. Aim 2: To develop and pilot test an assessment protocol for dementia screening for adults with ASD. It is anticipated that findings from this supplement will form the basis for a larger exploration of the course of aging and dementia in adults with ASD.