The natural progression of autism into adulthood is an important but poorly understood topic. This is a comprehensive study of clinical and functional outcome factors in 169 adults with Autism Spectrum Disorder (ASD) to complement the research group's recently begun epidemiologic study of 326 adults with autism. In general, the sample is higher functioning (2/3 have IQ above 70) than the currently funded epidemiologic sample, reflecting the modern trend of diagnosing individuals with higher functioning abilities. The investigators have extensive historical assessments on these adults dating back at least 5 years for most and 10 years for many. The combined sample will provide a more comprehensive look at critical unknowns regarding the developmental trajectory of adults with ASD, including mortality, co-morbidities, and functional outcomes. This study will also improve the capacity to suggest upcoming obstacles and needs for the "epidemic" cohort of children with autism approaching adulthood. It proposes combining and comparing current outcome data from the proposed adult group, first assessed in the late 1990s, with the currently funded epidemiologic group first ascertained in the 1980's. The study is designed with additional power to study subgroups dissecting specific outcomes. It also assess co-morbidities, and markers of functional outcome for the combined sample (n=439) using computerized hospital discharge and vital statistics data contained in the Utah Population Database. Finally, the researchers will address the transition experience from school-based to adult services and situations through direct assessment of relevant factors in a subgroup of 114 participants, aged 17-25. They anticipate that approximately 85% of this proposed sample (n=145) will participate in direct assessments. These additional subjects will add substantially to our ability to understand developmental subtypes with specific outcomes. These studies will provide crucial information about important treatment and service opportunities that will promote better quality of life for adults with autism, their families, and society. In addition to disseminating results about adult functioning and developmental trajectories, it will develop a unique resource for future studies of autism in adulthood.