Mycoplasma Hoechst Stain Kit is designed for rapid in situ detection of mycoplasma, and other prokaryotic organisms, in cell cultures in less than two hours. This procedure is based on the Hoechst Stain method cited by the Tissue Culture Association (TCA Procedure No, 75361). Several DNA fluorochromes such as DAPI, quinacrine mustard and quinacrine dihydrochloride have been used in the same technique but none of the fluorochromes perform as well as the Hoechst stain with respect to fluorescent effect, slow quenching and minimum background fluorescence. The Hoechst Stain method selectively binds minor grooves of the DNA, which allows for efficient staining of the nuclei.