In some cases of treatment-resistant chronic mental illness, it may be useful to reconsider the primary diagnosis. Patients with Asperger's syndrome, a rare pervasive developmental disorder, have characteristics such as eccentricities, emotional lability, anxiety, poor social functioning, repetitive behavior, and fixed habits that can mimic symptoms of other illnesses, including schizophrenia spectrum illness, bipolar disorder, anxiety disorders, and obsessive-compulsive disorder. Their disorganizing anxiety in response to stress, which may be accompanied by increased oddness of speech, can easily be misinterpreted as psychosis. The author describes features of Asperger's syndrome, discusses differential diagnosis, and presents care examples. A habilitative treatment plan that concentrates on modifying the patient's eccentricities into strengths and carefully tailors the work and living situation may be effective with some patients.