Autism and Asperger syndrome are disorders with early childhood onset. They are believed to exist on the same spectrum of impairments of reciprocal communication and social interaction restriction of imagination and behaviour. A number of screening and diagnostic tools have been developed in the field, and several of these are briefly reviewed here. It is concluded that autism may be screened around age 18 months and a diagnosis reliably be made around age 30 months, whereas a diagnosis of Asperger syndrome is not usually suspected, screened or made until into the child's school age.