This chapter focuses on Thin-layer chromatography (TLC) assays for the study of lipid receptors of bacteria and bacterial proteins, including purified toxins and "adhesin" proteins that mediate bacterial adhesion. TLC has been an indispensable tool for investigations concerning host lipids that function as receptors for microbial pathogens and their toxins. Radiolabeled cholera toxin was the first protein ligand used in the TLC overlay that demonstrated unequivocably that cholera toxin used GM1 as a receptor. There are several factors to be considered in choosing TLC plates, including cost, efficiency of resolution of the compounds under study, and the amount of sample available. For preparative TLC, the lipid sample is applied as a long band across the bottom of the plate with spots of standard lipids at either end of the plate. TLC has had many applications in bacteriology in the area of the separation and identification of bacterial components. The majority of applications have been in the field of bacteriology.