Diagnostic ambiguities surrounding Asperger's syndrome are discussed in a historical context; two main subtypes are distinguished according to whether coping mechanisms are predominantly obsessional or schizoid. A case is reported of a girl, later diagnosed with Asperger's syndrome, who originally showed many characteristics of autism, including echolalia. In the later stages of her treatment, she resembled borderline children in her anxious outpouring of florid fantasy. The transition from the first stage to the second was marked by a fantasy of the bodily projection of her mouth into the therapist. Drawings from the beginning of treatment suggested that the schizoid fantasies characteristic of the second stage were already present, although in unelaborated form. The case is discussed in the context of object relations theory and of historical controversies concerning the relationship of autism to childhood psychosis. It is suggested that the intimate psychodynamic knowledge of a child acquired during therapy can make a contribution to diagnostic classification.