Immunodeficiency is frequently invoked as an ethiopathogenetic factor for many somatic diseases. On the other hand, stress, depression, and psychotic disturbances are associated with severe immunological disorders. Taking into account that the benzodiazepines (BZ) are the psychoactive drugs more widely used than any other to treat psychological disturbances, it seems important to elucidate the immuno-enhancing or immunosuppressant potential of such drugs. Our goal was easily reached, since 69% of the outpatients visiting our Institute are chronic BZ consumers and because neurochemical, hormonal, immunological, and psychiatric investigations are routinely performed on all of our patients. In the present study, immune function was investigated on two occasions: while the patient was on active medication and 15 days after discontinuation. We concluded that chronic consumption of BZ provokes significant immunological disorders that should be further investigated. Said disorders could not be linked to a pre-existing affective disease or psychosis, since we only selected those BZ users in whom psychiatric investigations ruled out a past or present history of major psychiatric disease.