Ultrathin films of graphite-polymer composites, which are required for sensors applications, are the target of the work reported here. The preparation and characterization of ultrathin films composed of self-assembled graphite oxide (GO) platelets and polyelectrolytes are described, followed by the in situ reduction of GO to a conductive graphite-like state (G) by chemical and electrochemical methods. Particular attention is paid to the non-conductive to conductive transition that occurs on reduction and the behavior of incorporated CdS particles.