This chapter describes the methodology by which mAb-F19-conjugated gold nanoparticles were prepared and used to label human pancreatic adenocarcinoma. Specifically, gold nanoparticles were coated with dithiol bearing hetero-bifunctional PEG (polyethylene glycol), and cancer-specific mAb F19 was attached by means of NHS-EDC coupling chemistry taking advantage of a carboxylic acid group on the heterobifunctional PEG. These conjugates were completely stable and were characterized by a variety of methods, including UV–Vis absorbance spectrometry, darkfield microscopy, DLS (dynamic light scattering), TEM (transmission electron microscopy), SEC (size-exclusion chromatography), and confocal microscopy. Nanoparticle bioconjugates were used to label sections of healthy and cancerous human pancreatic tissue. Labeled tissue sections were examined by darkfield microscopy and indicate that these nanoparticle bioconjugates may selectively bind to cancerous tissue and provide a means of optical contrast.