This review reports the literature survey of 1,2,4-triazepines. The investigated heterocycles are monocyclic and fused 1,2,4-triazepines. The different sections cover theoretical calculations of conformations and tautomerism, and synthesis and reactions of monocyclic and fused heterocycles incorporating 1,2,4-triazepines. The biological evaluation of the target compounds and related compounds is described, as well as the synthetic applications. The reaction mechanisms are discussed. The bibliography includes 152 references.