A strip theory approach is described which is designed to obtain the lift and drag coefficients of a wind turbine rotor operating as an autogyro. This theory is an extension of the autogyro theory which was developed during the 1920’s and 1930’s. The theory has been extended to include the effects of varying blade planform, blade section and blade twist. This was necessary in order to evaluate the performance of the variable pitch rotors used for the propulsion of marine craft when operating in beam winds in the autogyro mode. Rotors with flapping blades were not considered. A computer program has been written incorporating this method. Results have been obtained for two example autogyro rotors using this program and these are presented here to give an idea of the typical performance of a wind turbine rotor when operating in the autogyro mode. The characteristics of autogyros are discussed in relation to their use as propulsion systems for wind propelled marine vehicles.