The diagnosis and treatment of psychiatric disorders in intensive care patients have been for a long time neglected. They are nowadays better recognized and managed. These disorders are mainly: delirium; anxiety disorders, from simple anxiety to panic disorder with agitation; adaptation disorders with depressive mood; brief psychotic disorders with persecution ideas. The manifestations of psychiatric disorders occur not only during the stay in intensive care unit (ICU) but also after transfer from ICU and several months after discharge from hospital. Part of psychiatric disorders is caused by organic or toxic causes (metabolic disturbances, electrolyte imbalance, withdrawal syndromes, infection, vascular disorders and head trauma). Nevertheless some authors estimate that they are due to the particular environment of ICU. The particularities of these units are: a high sound level (noise level average between 50 and 60 dBA), the absence of normal day-night cycle, a sleep deprivation, a sensory deprivation, the inability for intubated patients to talk, the pain provoked by some medical procedures, the possibility to witness other patients' death. Although most patients feel secure in ICU, some of them perceive ICU's environment as threatening. Simple environmental modifications could prevent the apparition of some psychiatric manifestations: efforts should be made to decrease noise generated by equipment and staff conversations, to provide external windows, visible clocks and calendar, to ensure adequate sleep with normal day-night cycle and to encourage more human contact. Psychotropic drugs are useful but a warm and empathetic attitude can be very helpful. Some authors described specific psychotherapeutic interventions in ICU (hypnosis, coping strategies.). To face anxiety, many patients have defense attitudes as psychological regression and denial. Patient's family is suffering too. Relative's hospitalization causes a crisis in family. Unpredicted illnesses often force family members to reorganize in order to regain their equilibrium. Every family should be proposed a psychological support. Caregivers can be distressed as well. This stress is due to their high responsibility and the fact that they face disease and death. Simple measures can lessen stress'effect and prevent the burn-out syndrome . In conclusion, the importance of a liaison psychiatrist-intensive care physician collaboration must be emphasized in order that patients and their family have a better psychological support. Psychological management should be proposed during the hospitalization and after discharge from hospital.