We have developed an algorithm for analysis of angle-resolved x-ray photoelectron spectra that allows quantitative depth profiling of the surface elemental composition with atomic depth? resolution. This method has nondestructively yielded valuable new information about adsorbate bonding and conformation for several of the chemical systems listed below, permitting adsorbate modeling at the atomic level. The computation implements a profile-smoothing search and gives error limits on the profiles. The method is capable of computing at least six simultaneous elemental profiles, is robust to as much as 10% experimental error, and performs well even under unfavorable conditions such as patchy overlayers, complex organic adsorbates (such as DNA), and trace elemental quantities (<10%). The depth profiles obtained for Cu on Ru(0001), SiO2 on Ag(111), and for sulfur-modified DNA, CI(CH2)(3)SH, and cystamine adsorbed onto Au(lll), show close correspondence to scale molecular models and to expected stoichiometries for the surface composition.