Experimental insight derived from the measurement of heat transfer rates is useful in a number of engine-related activities-ranging from developing simulations for predicting engine performance to defining cooling requirements for insuring the integrity of engine materials. Consequently, a device for measuring steady-state heat-transfer rates in a solid was designed after an extensive heat-transfer analysis. Subsequent experimentation and development has led to an accurate miniature sensor which can be installed directly into a parent material with little thermal disturbance. An analytical model of the sensor, installed in the combustion chamber wall of an engine, predicted this disturbance error to be 3% or less over a wide range of parent material properties and engine operating conditions. Experimentation at four heat-transfer rates confirmed this predicted performance. Although motivated by engine development programs, this heat-flux sensor is potentially applicable to a broad range of experimental investigations.