Ten patients in a Veterans Administration hospital who had been diagnosed and treated as schizophrenic were rediagnosed as having bipolar affective illness and were shown to be responsive to lithium. The authors feel that the diagnosis of schizophrenia is made too frequently and often is made with inadequate information. A further complicating factor in diagnosis is that some patients exhibit schizophrenia-like symptoms during the acute manic phase. The authors found that valuable aids to rediagnosis of such patients include a good premorbid and interepisodic adjustment, a history of depressive episodes, a family history of affective disorder, and a favorable response to a therapeutic trial on lithium carbonate.