This article examines the problems of foreign language interpreting in psychiatric practice. It is demonstrated how an interpreter's apparent competence may readily be mistaken for true competence and that it is well worthwhile formally assessing an interpreter's command of his second language. In interpreting from patient to psychiatrist, the omission of important material was found to be a noteworthy feature. Here the meaninglessness of material not only favoured its omission but also often indicated important psychopathology. It was found that the more psychotic the patient the more likely it was that mistakes in interpreting from patient to doctor would occur.