CD107a, also known as the lysosome associated membrane protein-1 (LAMP-1), is expressed largely in the endosome-lysosome membranes of cells, but is also found on the plasma membrane (1-2% of total LAMP-1). LAMP-1 has been implicated in a variety of cellular functions, including cancer metastasis. It has been proposed as a therapeutic agent for some cancers, and is a marker for lysosomal storage disorders and different cell types such as cytotoxic T cells. In light of this diversity of applications, it is important to have well characterized immune-reagents for the detection and quantification of LAMP-1. We have compared a new monoclonal antibody 80280 against LAMP-1 to an existing monoclonal antibody BB6 and a rabbit polyclonal antibody. While all antibodies gave similar results by immunofluorescence, the monoclonal antibody 80280 showed no epitope reactivity to LAMP-1 peptides, suggesting the possibility of a carbohydrate epitope. Western blotting revealed a weaker activity of the monoclonal antibody 80280 relative to either the BB6 monoclonal or the polyclonal antibodies. The monoclonal antibody 80280 is distinct from BB6, providing an additional reagent for CD107a analysis.