A procedure for designing quantitative echo sounders, whose main purpose is fisheries resource surveys, is described. The quantitative echo sounder must be designed under the specific criteria, such as minimum error, taking into account the purpose, external conditions, and several acoustic characteristics. The acoustic characteristics needed in the design procedure, for example, the scattering properties of fish, are reviewed briefly. In the main part, the method to determine the pulse width, bandwidth, operating frequency, transducer diameter, and gain allocation for each stage of the receiver is described. A convenient ‘‘universal diagram’’ is introduced for determining the basic parameters. The diagram serves also for users of sounders. Application of the method to two kinds of sounders is demonstrated. The optimum frequency for quantitative echo sounders is discussed and the frequency of 38 kHz, being used worldwide, is shown to be a reasonable frequency.