Images have been obtained of two types of chimeric B72.3 anti-TAG-72 mutant hinge IgG4 antibodies using scanning tunneling microscopy. The antibodies were specifically engineered to show differences in their conformation due to site specific modifications in their hinge regions. To overcome initial difficulties due to tip sweeping effects, the method of immobilization employed was spray deposition on mica followed by rotary shadowing with platinum/carbon (Pt/C). Topographic data were obtained, and differences between the two mutant forms of the antibody were clearly visible.