Over the past decade, the reported incidence of autism spectrum disorders has continued to increase. Coincident with this, the number of referrals to clinical geneticists to identify the etiology has also dramatically increased. The reported diagnostic yield for autism spectrum disorders is commonly reported in the range of 6-15%. However, continued advances in genetic technology expand the diagnostic options available for these evaluations and presumably increase the diagnostic yield. The list of genetic and metabolic conditions that have been reported with an autism phenotype is quite extensive. In deciding on an evaluation plan, the clinical geneticist has the difficult task of balancing an ever-expanding list of available tests and possible diagnoses with the issues of cost, practicality, and expected yield. In this article, we discuss a strategy of a tiered evaluation of the etiology of autism. These recommendations use evidence-based conclusions from the current available literature and cumulative clinical experience.