Twin and family studies have established that there is a strong genetic basis for autism spectrum disorders. To facilitate the identification of susceptibility genes and to study pathways from gene-brain to cognition a more refined endophenotype-based approach may be useful. The purpose of the present study was to examine the neurocognitive endophenotype of autism, in families with multiple incidence autism. Eighty-six members of 18 families containing at least two individuals with autism were neuropsychological assessed. Children with autism, showed weak central coherence, but this "trait" could not be found in their parents nor in non-affected siblings. All family members, including the sibpairs with autism, showed deficits within executive functions, involving planning ability, but normal set-shifting. The sibpairs with autism--but not their other family members--showed significant correlations within two visuo-spatial tasks. Deficits in executive functions (specifically planning ability) appear to characterize the broader endophenotype of autism. Our findings do not confirm the hypotheses of weak central coherence or deficits in theory of mind as part of the broader endophenotype of autism. Deficits in visual scanning may be a feature of the manifest phenotype of autism. (Contains 3 tables.)