Occipitofrontal circumference (OFC), measured at birth and after 16 months of age, was compared in 50 consecutive patients with Asperger syndrome, 50 diagnosed with autistic disorder, and 50 with ADHD and followed at the Department of Child and Adolescent Psychiatry, Goteborg University, Sweden. All three groups had mean OFCs at birth and after age 16 months that were larger than normal. Asperger patients’ mean OFC was significantly greater than that of the autistic group and the ADHD group. Macrocephaly (defined as OFC >2SDs and height and weight 1SD below that expected for the OCD) was present in 11 of 43 Asperger patients at birth and in 9 of 43 after 16 months. Corresponding rates were 4 of 42 in the autistic group, and 7 of 47 in the ADHD group at birth. Significant correlations between OFC at birth and after age 16 months occurred in the Asperger but not in the autistic or ADHD groups. OFC and IQ were not correlated. Two children with Asperger syndrome who had suffered perinatal asphyxia had microcephaly. Autistic spectrum disorders included a subgroup with macrocephaly and a relatively high level of functioning, with clinical presentation consistent with Asperger syndrome. 
COMMENT. One in 4 children with Asperger syndrome and 1 in 10 of those with autistic disorder have macrocephaly when examined after 16 months of age. Among autistic children, macrocephaly is more typical of the highest functioning variant, Asperger syndrome, and is not characteristic of the moderate to low-functioning autistic spectrum disorder.