At present, combustion pressure sensors find widespread use in basic engine research and development. In the future they could provide the essential information for closed loop engine control (of both fuel mixture and ignition timing) and diagnostics. The quartz piezoelectric device is the most familiar; its concept has been extended to piezo-ceramic configurations seated beneath or inside a sparkplug. This paper presents preliminary results for a novel fiber-optic pressure sensor incorporated into a spark-plug. Head-stud transducers are also described.