Over the years several methodologies have been developed for the structural analysis of naturally occurring sialic acids (Sias), a family with more than 62 members. Currently there are two primary instrumental approaches: analysis of volatile Sia derivatives by gas-liquid chromatography (GLC) combined with electron-impact mass spectrometry (EI/MS), and analysis of fluorescently labeled Sias by high-performance liquid chromatography (HPLC) eventually coupled with electrospray mass spectrometry (ESI/MS). This chapter presents both approaches in detail. The volatile Sia derivatives are comprised of trimethylsilylated methyl ester derivatives, heptafluorobutylated methyl ester derivatives, or pertrimethylsilylated derivatives. The fluorescent Sia derivatives are prepared by reaction with 1,2-diamino-4,5-methylenedioxybenzene. For the identification of the different Sia derivatives, detailed GLC, HPLC, EI/MS, and ESI/MS data are included.