The widespread use of BDZ is due on one hand to its therapeutic effectiveness, particularly as a tranquillizer, hypnotic, myorelaxant and antiepileptic, and on the other to its few side and toxic effects. Long-term treatment with BDZ has, however, proved to be not completely free from problems and particular attention has been paid to these in recent years. These negative aspects, described by the literature, include global worsening of mental activity and a declining efficiency of certain mental functions; also worth considering are the phenomena related to the onset of addition and dependence.