Surface derivatization with trifluoroacetic anhydride (TFAA) on self-assembled monolayers of 16-mercapto-1-hexadecanol (MHD) was studied to develop selective and well-defined methods for the surface modification of biomaterials. The terminal hydroxyl groups of;MHD were functionalized by both solvent- and vapor-phase reactions. The reaction kinetics, accessibility, and reactivity of SAMs with different surface coverages and film structures were investigated via complementary surface analytical techniques (external reflection-absorption FTIR, XPS, and TOF-SIMS). The TFAA derivatization reaction exhibited rapid kinetics on the hydroxyl-terminated SAMs. The data from each of the surface analytical techniques consistently indicated a nearly complete surface reaction. This suggests that the trifluoromethyl ester group did not introduce significant steric hindrance. The high accessibility and reactivity of TFAA derivatization on hydroxyl SAMs is related here to earlier studies on polymer systems.