Adsorption of HIV protease onto surfaces that are usually considered to be protein-resistant was studied quantitatively using surface plasmon resonance. Adsorption onto gold surfaces functionalized by OH-terminated alkyl chains was much stronger than onto oligo(ethylene glycol)-terminated surfaces. Equilibrium and kinetic adsorption constants were determined. An anomalous mutual attraction between adsorbate molecules was observed, indicating the possibility of two-dimensional crystallization of HIV protease. These results are applicable for the design of sensors/biosensors for HIV protease resistance detection and for proper manipulation of this enzyme in laboratory devices.