The ability of a "tumor-specific', monoclonal antibody (OX7) and a subclass-matched, non-specific, control antibody (anti HRP) to localize in and image small (20-60 mg) murine lymphomas growing in the subrenal capsule of mice was tested. Due to the small tumor size, and its visceral location, the subrenal site of tumor growth represents a model of metastases which may be more clinically relevant to human cancer. The in vivo and in vitro quantitative data (as well as the gamma camera images) support the feasibility of the concept of using monoclonal antibodies for metastatic tumor detection and treatment.