CF568 streptavidin conjugate is prepared from high quality streptavidin and the fluorescent dye CF568. CF568 (Ex/Em = 562/583 nm) is a red fluorescent dye with an excitation spectrum optimally matching the 568 nm line of the Ar-Kr mixed-gas laser. Antibody conjugates of the dye are much brighter than those of Alexa Fluor? 568. In addition, the photostability of CF568 is superior to that of Alexa Fluor? 568, making CF568 a much better choice for demanding applications, such as confocal microscopy and single molecule imaging.