Graphite is a highly anisotropic crystal with a quasi-two-dimensional electronic structure exhibiting high intrinsic charge carrier mobility. Here, we investigate the effect of an electric field on the resistance of individual graphite crystallites with a thickness on the order of 40 nm. Ambipolar field-effect behavior was achieved with the aid of a polymer electrolyte gate. By optimizing the device geometry, devices with an on/off current ratio of up to 4 and carrier mobilities of around 100 cm(2)/Vs could be attained directly on the crystallites. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4719204]