Efforts to evaluate and discover diagnostic and therapeutic markers for prostate cancer continue. One of these, prostate-specific membrane antigen (PSMA), a transmembrane protein expressed in all types of prostatic tissue, remains a useful diagnostic and possibly therapeutic target. The radio-immunoconjugate form of the anti-PSMA monoclonal antibody 7E11 is used in the commercially available and US Food and Drug Administration-approved diagnostic tool, the ProstaScint®(Cytogen Corporation, Princeton, NJ) scan. Recent studies have demonstrated other possible useful roles for PSMA as a target, not only in prostate cancer, but in other malignancies.