Automobile brakes contain friction materials which by definition will wear as the brakes are being used and require replacement to prevent failure or damage to the brake system.In addition to the brake friction materials, the hydraulic and mechanical systems involved in brakes of automobiles deteriorate over a period of time. This deterioration occurs at a rate which requires several reiterations of repair throughout the life of the vehicle.Wear rates change significantly depending on driving habits, vehicle design and geographic and climate conditions of use. This variation makes it difficult if not impossible to predict with any accuracy when parts of the brake system require maintenance or replacement.In order to avoid dangerous brake failures and expensive repairs caused by deterioration, it is desirable to monitor the status of brakes. Current methods for doing this are limited.The object of this paper is to present the present state-of-the art of monitoring passenger car brake systems and to describe how this is being accomplished by on-board sensors. A more comprehensive “off board” monitoring system which is being developed by Avco is also described.As a result of this study, the automobile engineer will have a better understanding of the type of modifications which may be required to improve the brake-related safety aspects of automobiles and decrease brake maintenance costs.