The possibility of conversing, listening to radio or calling on the phone is a factor (constituent) of comfort within automotive vehicles. It is not possible to deny that correct conditions of speech intelligibility are seldom fulfilled. The study started by INRETS-LESCO, under a contract with PSA-RENAULT, intends first to acquire knowledge of frequency components of the noise perceived in the occupant compartment of a motor car depending on car speed, occupant location and road surface. The measurement of perceived noise is gained from a previously developed methodology.At the same time, research dealing with tests and indices of intelligibility to be used in a motor car compartment has been started. Following the evaluation of the various indices -measured or computed (global) acoustical indices and subjective indices obtained from the jury method-, the aim is in the near future to work out a reliable method of laboratory tests and later on to propose a definitive and easy process for assessing intelligibility in motor vehicles.