This study investigated the reliability and stability of an autism diagnosis in children under
3 years of age who received independent diagnostic evaluations from two clinicians during
two consecutive yearly evaluations. Strong evidence for the reliability and stability of the
diagnosis was obtained. Diagnostic agreement between clinicians was higher for the broader
discrimination of autism spectrum vs. no autism spectrum than for the more specific
discrimination of autism vs. PDD-NOS. The diagnosis of autism at age 2 was more stable
than the diagnosis of PDD-NOS at the same age. Social deficits and delays in spoken
language were the most prominent DSM-IV characteristics evidenced by very young
children with autism.