Diagnostic communication between doctors and patients is thought to differ radically between Japan and Western countries. To understand diagnostic disclosure to psychiatric patients, a questionnaire with six case vignettes was sent to practising psychiatrists in Japan (N = 166) and North America (N = 112). While over 90% of both groups would inform patients with affective and anxiety disorders of their diagnoses, only 70% of North Americans and less than 30% of Japanese would similarly inform patients with schizophrenia or schizophreniform disorders. The Japanese preferred alternative was to give a vague alternative diagnosis such as neurasthenia. North Americans would discuss differential diagnoses with the patient instead. Nearly all in both groups would inform the family, but North Americans would do so only with patient consent. For disorders for which there are effective treatments, diagnostic disclosure is common to both cultures; when prognosis is uncertain or the diagnosis is feared, as in schizophrenia, culturally constructed views of patienthood govern disclosure practice.