An introductory review of the equivalent electric circuit of a piezoelectric vibrator and its parameters is followed by a discussion of the determination of these parameters by the transmission method. This method was published in 1951 and became the basis for the 1957 IRE Standard. Since that time, a thorough investigation of the transmission method has resulted in more precise expressions which permit a more accurate evaluation of the parameters. This method is suitable for frequencies up to about 30 MHz for the commonly encounted ranges of the capacitance ratio r and the figure of merit M, provided that errors due to instrumentation are taken into account. The equations presented in this Standard have been formulated to correct these errors.<>