Autism spectrum disorders (ASD) have a complex genetic component comprising both frequent polygenic and rare monogenic factors. Research is conducted in methods used to calculate polygenic risk scores, which are not applicable in clinical practice. Advances in genomic technology have identified several monogenic causes, and genetic testing may be offered to persons with ASD where a monogenic etiology is suspected. Herein, we provide an overview of the current knowledge and present the first national recommendation regarding genetic testing in ASD.