Four patients admitted to hospital with multiple injuries developed psychiatric symptoms after an initially favourable response to intensive therapy. Alterations in the level of consciousness and behavioural pattern were observed, associated with the presence of acute depression, possibly endogenous in origin. Within 24--48 hours of intravenous administration of maprotiline mesylate (Ludiomil, Ciba), a tetracyclic antidepressant drug, considerable improvement was noted in all 4 patients, with regard to both the depressive state and the clouding of consciousness. The importance of recognizing psychiatric disorders in severely ill patients in an intensive therapy environment is stressed.