Multiphoton ionization of atoms in intense laser-light fields is gaining ground as a spectroscopic diagnostic tool. In this volume, Delone and Krainov present their and others' theoretical descriptions of the processes occurring in atoms under conditions of multiple-photon impacts, in particular, the shift, broadening, and mixing of electronic states, which complicate the interpretation of spectra. The intended audience is the experimental physicist or physical chemist facing the task of unraveling an atomic multiphoton ionization spectrum. Comparisons of the theory to available experimental data are provided throughout. The topics of individual chapters include tunneling ionization, above-threshold ionization, ionization of multiply charged ions, resonance-enhanced ionization, super-intense radiation fields, and properties of Rydberg states in strong fields