In the last years autoradiography has gained greater importance as a quantitative method of measuring radioactivity or element concentration. Usually a relative measurement is used. The optical density of the photographic emulsion produced by a calibrated irradiation source is compared with that produced by a sample. The influence of different parameters, such as β-particle energy, backscattering, fading of the latent image, developing conditions, matrix effects and others on the results and the errors of the quantitative evaluation of autoradiograms are described. This method is demonstrated in the case of the quantitative determination of the gold content in silicon.