Micronucleus technique used to evaluate the degree of chromosomal damage at single cell level . Micronuclei originate from chromosome fragments or whole chromosomes that are not separated during cell division . This method is easy to use in human lymphocytes and thus suitable to conduct monitoring studies on human populations. It is now widely used to assess the effects of environmental, genetic factors and lifestyle on genetic stability . In this paper describes the basic principles underlying this method, including the method of counting and evaluation criteria for micronuclei . We also reviewed selected items of literature, in which the frequency of micronucleus was used as a biomarker of cancer and other degenerative diseases . Also discusses the impact of metabolic genotypes on various biological markers of genotoxic risk of exposure to environmental and occupational factors .