A brief discussion of the problem of measuring temperatures in jet engines is given. A method of measuring these temperatures by pneumatic means is described. This method involves the use of two sonic-flow orifices in series to give, through thermodynamic calculations, the total temperature of the gas entering the first orifice. An evaluation of this method is given including a discussion of the sampling error in nonhomogeneous gases, and an experimental comparison against a thermocouple and the sodium D-line reversal method is made showing favorable agreement. Results of applying this method of measuring temperature in full-scale engines are discussed.