A 14-year-old boy with mild mental retardation and behavioral features suggestive of the so called Asperger's syndrome is described. From the age of 8 years he has had recurrent episodes of lethargy. At the onset of puberty these episodes took on a more dramatic form and became more reminiscent of cycloid/manic-depressive psychosis. There is a family history of manic-depressive disorder. Neurobiological links with and differences from the syndrome of infantile autism were found. It is suggested that there is still too little evidence clearly to single out the entity of Asperger's syndrome from the spectrum of autistic syndromes.