Gold nanorods have been stabilized, conjugated to antibodies, and characterized for biological applications. The stabilizing surfactant bilayer which surrounds gold nanorods was replaced by thiol terminated methoxypoly(ethylene glycol) so that the nanorods are stable in buffer solutions free of surfactant. Nanorod bioconjugation was accomplished with a heterobifunctional cross-linker, with antibody activity confirmed by a strip plate assay. Nanorod bioconjugates were characterized by independent measurements of the nanorod and antibody concentrations. The nanorod molar extinction coefficient was measured from dense yet well separated nanorod films to be 4.4 ± 0.5 × 109 M-1 cm-1, thus allowing quantitative determination of nanorod concentrations. However, a colorimetric protein assay overestimated the antibody concentration and is therefore likely perturbed by the presence of the nanorods electromagnetically and/or chemically.