The ultrasonic harmonic generation technique employing fundamental and third harmonic wave amplitude measurements has been used to study the nonlinear elastic properties of SrTiO3single crystals. A complete set of nonlinearity parameters calculated from room temperature data support the values recently reported for the harmonic generation technique in which fundamental and second‐harmonic amplitudes were measured. The temperature variation of the third‐order elastic constantC111in the range 103°–300°K was also measured by third‐harmonic generation methods and was found to agree well with the corresponding second‐harmonic result. The experimental technique in most cases involved overlapped pulses in the pulse‐echo wave train, and the results were found to agree well with measurements for the first pulse in the normal pulse‐echo pattern.