Serial analysis of gene expression (SAGE) is a molecular biology technique that was developed to measure the global gene expression levels. It has been applied successfully to characterize transcriptomes, compare the transcript levels between normal and diseased tissues, and uncover novel molecules within defined signal transduction pathways. A detailed description is presented in this chapter of the procedures involved to prepare the SAGE libraries. Protocols for automated sequencing and other standard molecular biology techniques can be found elsewhere, and thus are not included herein.