The neutral arachidonic acid derivatives N-arachidonoyl ethanolamine (anandamide or AEA), and 2-arachidonoylglycerol (2-AG) have been identified as endogenous ligands for the cannabinoid receptors. Additionally, these compounds have been identified as substrates of the second isoform of the cyclooxygenase enzyme (COX-2). Through the action of COX-2 and downstream prostaglandin synthases, a diverse family of prostaglandin glycerol esters (PG-Gs) and prostaglandin ethanolamides (PG-EAs) have been identified. Sensitive and reliable analytical methodology is crucial for the continued research on the biological roles of this family of lipids. In this chapter, we discuss methods for analyzing both the precursor endocannabinoids and their PG-like products by LC-MS-MS. Cation coordination provides the ionization, and selected reaction monitoring is successfully employed to provide a method of analysis that is both sensitive and specific.