Western blotting is a technique that involves the separation of proteins by gel electrophoresis, their blotting or transfer to a membrane, and selective immunodetection of an immobilized antigen. This is an important and routine method for protein analysis that depends on the specificity of antibody-antigen interaction and is useful for the qualitative or semiquantitative identification of specific proteins and their molecular weight from a complex mixture. This chapter will outline the requisite steps including gel electrophoresis of a protein sample, transfer of protein from a gel to a membrane support, and immunodetection of a target antigen.