Porphyrins are a class of ubiquitously occurring compounds which are found in plants, animals, and microorganisms. Several physical and chemical techniques are available for the characterization, separation, and study of porphyrins. Coupled with chromatography, this is probably one of the most useful methods for characterizing an unknown porphyrin. The UV-vis absorption spectra of porphyrins are highly characteristic for this class of compounds. The application of infrared spectroscopy had been limited for many years to the recognition and characterization of side chains in porphyrins and metalloporphyrins. The most practical method for preliminary studies involving porphyrins is undoubtedly chromatography. For porphyrins, HPGC offers the only method for gas chromatography of these compounds as such. Detection of porphyrins is best done by visual observation of red fluorescent spots when the chromatogram is examined under long-wavelength UV irradiation in a dark room. Heme compounds are best visualized after spraying the chromatogram with an appropriate dye.