The development of selective photoionization of atoms is reviewed. This is a very general method for laser isotope separation, and it has extremely interesting spectroscopic applications. Processes tending to restrict the applicability of the method are discussed. Examples cited include the use of selective photoionization to study the superior structure in atomic spectra, the resonance transfer of excitation energy, and the spectroscopy of atomic Rydberg states. Questions involved in laser isotope separation by selective photoionization are discussed.