Graphene oxide is a hydrophilic derivative of graphene to which biological macromolecules readily attach, with properties superior to those of amorphous carbon films commonly used in electron microscopy. The single-layered crystalline lattice of carbon is highly electron transparent, and exhibits conductivity higher than amorphous carbon. Hence, graphene oxide is a particularly promising substrate for the examination of biological materials by electron microscopy. In this manuscript we compare graphene oxide films to commonly used amorphous carbon films, describing the use of graphene in optimizing the preparation of unstained, vitrified biological macromolecules. (C) 2009 Elsevier Inc. All rights reserved.