Heterocycles bearing nitrogen atoms constitute the core structure of a number of important physiologically active molecules and play a vital role in the metabolism of living cells. Benzodiazepines and their polycyclic derivatives are important class of bioactive compounds. This book centers around the synthesis of condensed nitrogen heterocyclic systems containing benzodiazepine nucleus, in this context it seems necessary to present a brief review of biological and the synthetic aspects of benzodiazepine and condensed benzodiazepine systems.