We present a clinical case of a 43-year-old female with progressive systemic sclerosis, Basedow's disease, atrial fibrillation and diabetes mellitus. She twice developed exacerbations of a psychotic state. She showed a depressive state followed by a paranoic hallucinatory state and stupor. Electroencephalograms revealed slow abnormal records both in psychotic and remitting periods and 123I IMP SPECT of the brain showed a low blood flow in the psychotic stage. A case of progressive diffuse sclerosis with a paranoic hallucinatory state is rarely reported. As her Basedow's disease had been well controlled, the psychotic symptoms of the present case are regarded as organic hallucinosis and organic delusional disorder due to progressive diffuse sclerosis.