Covalent modification of diamond surfaces with molecular monolayers serves as a starting point for linking biomolecules such as DNA and proteins to surfaces. DNA-modified diamond surfaces show excellent selectivity for hybridization with complementary vs. noncomplementary sequences and outstanding stability. These biomolecular recognition events also lead to changes in the conductivity of the interface via a molecular field effect in which the negative charge oil the DNA molecules alters the conductivity ill the diamond thin film. Chemical modification of the diamond with ethylene glycol oligomers leads to surfaces that effectively resist the nonspecific adsorption of proteins and other biomolecules to the surface. These outstanding physical and chemical properties of chemically modified diamond surfaces present new opportunities for the use of diamond thin films in biological applications. (c) 2004 Elsevier B.V. All rights reserved.