Aim: To describe cognitive and behavioural characteristics in a group of blind children with bilateral optic nerve hypoplasia (ONH). Methods: Data from records, parents, teachers, and repeated developmental assessments of 13 blind children with ONH born in 1988-1998 were analysed. All children had neuroimaging and/or hormonal evidence of midline malformations. They were all blind and able to communicate with speech. Results: Severe mood swings and temper tantrums were common, especially during the first years of life. Later in life, sluggish tempo, low frustration tolerance and a narrow range of interests were common. Autism had been diagnosed in 6/13 children, autistic-like condition (ALC) was found in another three. The behaviour of the remaining four children was not within the autism spectrum. Eight children had cognitive capacities within the normal or near- normal range; five had mental retardation. Autism/ALC was found in all cognitive subgroups. All children exhibited fluent speech and, of these, 12 had started to talk at the expected age, but had clear deficiencies in communicative ability. Conclusion: These children had a common pattern of behavioural characteristics including autism spectrum disorders independent of intellectual capacities. Aim: To describe cognitive and behaviologic characteristics in a group of blind children with bilateral optic nerve hypoplasia (ONH). Methods: Data from records, parents, teachers, and repeated developmental assessments of 13 blind children with ONH born in 1988-1998 were analysed All children had neuroimaging and / or hormonal evidence of midline malformations. They were all blind and able to communicate with speech. Results: Severe mood swings and temper tantrums were common, especially during the first years of life. Later in life, sluggish tempo , low frustration tolerance and a narrow range of interests were common. Autism had been diagnosed in 6/13 children, autistic-like condition (ALC) was found in another three. The behavior of the remaining four children was not within the autism spectrum. Eight children had cognitive energies within the normal or near-normal range; five had mental retardation. Autism / ALC was found in all cognitive subgroups. All children professed fluent sp eech and, of these, 12 had started to talk at the expected age, but had clear deficiencies in communicative ability. Conclusion: These children had a common pattern of behavioral characteristics including autism spectrum disorders independent of intellectual capacities.