Considerable debate still surrounds the question of whether the incidence of autism has risen over the last 20 years. Although numerous strategies for answering this question have been applied, the only way that this question can be settled is to go out into a set of communities and systematically screen an adult population of specified ages (such as 20-25), identify with high sensitivity (i.e., minimizing false negatives) a ‘suspected’ or possible autism group, follow-up this screening with a detailed assessment of autism and autism spectrum disorders in the suspected/possible ASD group, and obtain prevalence proportions for the specific ages surveyed. The focus of this meeting will be to evaluate the feasibility of using the household enumeration phase of the National Childrens Study to identify all persons, 20-25 years of age via their recruitment protocol . A short screening instrument will need to be developed to identify adults who may have ASD. This would have to be a rather short instrument, as a major criterion for approval of adjunct studies to the NCS is to not add undue participant burden. This screening would constitute the first stage, and those identified as being potential cases of autism would then undergo a further battery, to be scheduled at a later time, and possibly another location than the home. A workshop will be scheduled on April 24, 2008 which includes a dozen representatives of NCS sites, epidemiologists, clinicians and statisticians to determine the sample size necessary and budget required to engage in such an effort. A well designed, properly powered study will help to answer the following questions: has the incidence of autism truly risen over the last few decades? Specifically, it will address: what is the prevalence of autism in adults of a selected age range (e.g., 26-30) and how does it compare to children today (aged 6-10)?