Glycans located on the cell surface regulate cell-cell interaction, cell homing, and signal transmission, which are particularly important for communication among cells. Certain cell types contain unique cell surface glycan structures, which have been utilized as markers for characterization. Flow cytometry is a powerful technology that enables the examination of multiple parameters of individual cells (e.g., cell size, internal complexity, and surface marker expression level). In this chapter, we describe a step-by-step procedure on how to detect glycans on the cell surface of live cells by flow cytometer, using lectins.