A review is made of the current status of research on the nonlinear photoelectric emission resulting from the action of high-power laser radiation. The main experimental results are considered and possible theoretical interpretations are discussed. Considerable attention is concentrated on topics investigated recently, such as photoelectric emission in electrolyte solutions; photoelectric emission under the action of ultrashort laser pulses; detailed time, polarization, energy, and some other characteristics of photoelectric emission. Methods and results of calculations of the nonlinear photocurrent from the surfaces of metals are described. Theoretical results obtained by various methods are compared with one another and with the experimental data.