A recombinant, human monoclonal antibody targeting an extracellular epitope of human prostate specific membrane antigen (PSMA) that is conjugated with a fluorescent dye A488, with potential imaging activity. Upon intravenous administration, the MDX1201 moiety of anti-PSMA monoclonal antibody MDX1201-A488 targets PSMA expressed on cancer cells. Subsequently, the A488 moiety can then be visualized by fluorescence-based imaging and the amount of PSMA-expressing tumor cells can be assessed. A488 is a photostable fluorescent dye with a high quantum yield. PSMA, a tumor-associated antigen and type II transmembrane protein, is expressed on the membrane of prostatic epithelial cells and overexpressed on prostate tumor cells.