Numerical data from the literature on presbyacusis, in the form of pure-tone hearing threshold levels as a function of age, are subjected to critical evaluation and analysis. A formula is derived for predicting the age effect for otologically screened groups of males and females. Further, the complete distribution of hearing levels for each audiometric frequency in the range 0.125-12 kHz and at any age can be estimated with the aid of tabulated coefficients and some simple rules. The study was undertaken in connection with the work of ISO on standardization of normative audiometric data.