Living microorganisms when consumed in adequate amount confer many health benefits to host. Such healthy microorganisms, also known as probiotics, usually found in fermented foods and belongs to the category of generally regarded as safe category of microorganisms for human applications such as lactic acid bacteria. However, for any product to be used for human consumption, genotoxicity assays for evaluation of safety are necessary. Genotoxicity assay detects the ability of a chemical, physical agent, or any substance to induce damage to DNA. Several in vitro and in vivo assays are used to evaluate genotoxicity of substances. Mammalian spermatogonia chromosomal aberrations assay analyses chromosomal aberrations (both chromosome and chromatid type) in dividing germ cells, providing information on potential genotoxicity of the test compounds. This chapter describes a comprehensive method for assessing bacteria induced chromosomal aberrations in spermatogonia.