Racing thoughts, which have been previously described in schizophrenia and mania, were found to be equally prevalent in hospitalized depressed and manic patients. Racing thoughts are rare in schizophrenics who do not have an affective syndrome and more common in schizoaffective patients. The symptom is associated with disturbed concentration. It is experienced as pleasant by manic patients and as unpleasant by depressed patients. Racing thoughts may be important in the understanding of affective illness.