In this work, we have examined the influence of different parameters both on perceived saturation and saturation discrimination with unrelated colours, on the basis of S. L. Guth's CA90 colour-vision model and its subsequent modifications. Our analysis of perceived saturation covered (1) spectral saturation functions at constant luminance, (2) saturation functions in constant colorimetric purity loci, (3) saturation vs. colorimetric purity functions, (4) saturation vs. luminance functions in the 1-1000 td range, and, finally, (5) the equal saturation loci in the xy color diagram. Regarding saturation discrimination, we focused on (1) saturation thresholds from white and from the locus, (2) the number of just noticeable steps from white to the spectral locus as a function of dominant wavelength, and (3) the colorimetric purity incremental threshold vs, colorimetric purity at constant dominant wavelength. Hunt's 1991 colour-appearance model and the colour-discrimination model by Yeh et al. (1993) were used for comparison purposes. The behavior predicted by Guth's and Hunt's models is qualitatively very similar in many issues, but they especially disagree on the dependence of saturation on luminance. For the discrimination task, Guth's model pi-edicts spectral discrimination functions comparable with those predicted by Yeh et al., both from white and from the locus. Nevertheless, the models disagree on intermediate colorimetric purifies for most wavelengths. The model is basically consistent with the experimental data except for the luminance dependence. On the other hand, the literature on discrimination is insufficient to determine which model is right.