Piezoelectrics have recently gained popularity as an integral part of smart materials. Piezoelectric materials exhibit both direct and converse piezoelectric effects. The former effect, i.e. generation of an electric field as a response to mechanical strain, is employed in piezoelectric sensors. The latter effect, i.e. mechanical strain produced as a result of an electric field, is used in actuators. The converse effect is usually relatively weak in present-day piezoelectrics, limiting their applications as actuators. However, piezoelectric materials have been found to be both efficient and reliable in sensory applications. Temperature has a profound effect on the properties of piezoelectrics. Moreover, it affects the properties of the substrate (the structure whose response the sensor must monitor). The latter effect is particularly prominent if the substrate is manufactured from a polymeric composite material, because polymeric matrices are more affected by temperature than metallic or ceramic materials. These two effects, i.e. the effects of temperature on piezoelectric sensors and on a composite substrate, represent the subject of the present paper. It is shown that even moderate fluctuations of temperature within 200°C can significantly change the voltage reading from a piezoelectric sensor. Therefore, a reliable interpretation of data from piezoelectric sensors requires an engineer to account for thermal effects on the sensor and the substrate material. © 1996 IOP Publishing Ltd.