A short review is given of the basic chemical development in the field of 'classical' and 'annelated' benzodiazepines, distinguishing between pro-drugs and directly acting compounds. Some properties of midazolam that are of special interest for its practical use are discussed, such as: the basicity of its imidazole ring nitrogen, which allows water-soluble salts and well-tolerated aqueous injectable solutions to be prepared; its stability to hydrolytic degradation; its rapid metabolic inactivation, which is mainly determined by the methyl group on the imidazole ring, and which is much faster than that of classical benzodiazepines.