A commonly observed phenomenon in atomic-absorption spectrophotometry is the bending of the calibration graph y=f(c) towards the concentration axis (c) at elevated concentrations. Comparison among various alternative mathematical descriptions for these curves shows that an exponential description according to y=y_∞[1 – exp(–kc)] serves well in order to describe experimental calibration graphs. After optimisation of the instrumental settings, the numerical values of the two parameters y_∞ and k depend significantly on the atomisation temperature and the selected wavelength of the light source. Correlations between these two parameters and numerous other chemical and physical parameters of the elements to be assayed are shown to be non-significant. Based on the correlation between y_∞ and the wavelength, λ, a hypothesis is presented. It describes the intensity of the light beam passing through the atomic cloud by light absorption according to the Beer-Lambert law and by Rayleigh scattering at clusters of atoms. The experimental results presented for seven elements support this hypothesis.