Despite sharing a common set of behaviors, persons with autism spectrum disorders (ASDs) vary widely. This variation has made targeted treatment development difficult. The development of ways to subgroup persons with ASDs based upon biological data would be useful to ASD treatment development. Extracellular signal-related kinase (ERK) is an enzyme (protein) that plays important roles in brain cell signaling and growth. ERK activity is known to be abnormal as measured in the blood of persons with fragile X syndrome (FXS), a common single gene cause of autism. Recent finding from ASD research all point to potential ERK abnormalities in persons with ASDs of unknown cause. ERK activity has to date not been measured in persons with ASDs of unknown cause. This proposal aims to help develop better a better means to define potential subgroups of people with ASDs who may respond to specific treatments by measuring ERK activity in the blood of persons with ASDs. This proposal will take the first step towards studying ERK activity in ASDs by studying ERK activity in blood samples from 36 persons with ASDs (divided equally into 5-11, 12-17, and 18-25 year old groups) compared to values in control subjects who are IQ-, gender-, and age-matched to the participants with ASDs. Subjects with ASD and intellectual disability will also be matched to an age- and gender-matched neurotypical peer so we can help determine if any ERK abnormalities are related specifically to ASDs or more generally to intellectual disability. This project will provide the initial information needed to continue to develop study of ERK activity in ASDs including potential use of ERK study in targeted drug treatment studies as a means to determine which patients may most benefit from a potential new treatment.