The adsorption-induced Fermi level pinning is shown to occur at the coverages Θ* corresponding to a shallow extremum or saturation of the work function of the system. Equations for Θ* are derived within a modified Anderson-Newns adsorption model. Experimental data on the adsorption of atoms of alkali, alkaline-earth (Ba), and rare-earth metals and hydrogen on semiconductors (silicon, gallium arsenide, and titanium dioxide) are analyzed. The position of the Fermi level on the surface of a semiconductor is estimated.