Dyestuffs are of major environmental interest because of their widespread use as colorants for e.g., textiles, paper, leather, and foodstuffs. Synthetic intermediates, by-products and degradation products could be potential health hazards because of their toxicity or carcinogenicity. Most dyes, including sulfonated azo dyes are nonvolatile or thermally unstable, and therefore, are not amenable to gas chromatography (GC) or gas phase ionization processes. Thus, GC/MS techniques cannot be used. However, the combination of liquid chromatography (LC) with mass spectroscopy (MS) enables the separation of nonvolatile, thermally unstable, and polar dyes for introduction into the MS for identification. As a result of interfacing LC with MS, three major types of interfaces and LC/MS techniques have been developed: (1) Thermospray, (2) Particle Beam, and (3) Ion Spray and Electrospray. This chapter describes the application of these LC/MS techniques in the analysis of dyes.