This paper presents a theoretical and experimental study of the effect of cut-off control on engine performance. Cut-off control is an alternative method of load regulation in spark ignition engine. During cut-off operation, the charge is admitted at wide open throttle, hence the inlet charge passage is to be shut down before the completion of intake stroke. Cut-off is to be attained by means of an additional rotary valve mounted in series with the conventional inlet valve. The study indicates that cut-off control can provide a significant improvement in fuel economy. The effect of some important design parameters is also considered.