The excitation and emission spectra of carboxyrhodamine 6G (CR 6G) fall between those of fluorescein and tetramethylrhodamine. With a peak absorption at 525 nm, conjugates of carboxyrhodamine 6G are an excellent match to the 514 nm spectral line of the argon-ion laser. The amine-reactive 6-CR 6G, SE can be used to attach this fluorophore to biomolecules of interest including amine-modified oligonucleotides.