Metronidazole, a synthetic derivative of nitroimidazole, has been used in treatment of bacterial and protozoal infections. Particularly valuable is its bactericidal effectiveness against most anaerobic bacteria. Metronidazole is a valuable antimicrobial agent in the treatment of gastrointestinal infections, gynecological infections, anaerobic infections, such as bones, joints and soft tissues, as well as it is also commonly used in surgical prophylaxis. Adverse reactions are not threatening, but annoying. The interaction with alcohol can cause disulfiram-like reaction. Drug interference in the activity of CYP 450, may limit treatment options associated with several drugs. Described in animal studies, mutagenic and carcinogenic effects of metronidazole has increased concerns about its potential carcinogenicity in humans. Clinical and laboratory studies are aimed at indicating the adverse consequences of metronidazole therapy in the form of the development of the neoplastic process and to determine a possible cellular mechanism of inducing cancer.