A critical review and comparison of the initiation of combustion processes by conventional electric spark or thermal means with laser sources is presented. A description of the fundamentals of ignition processes is used as the basis for interpretation of experimental and theoretical studies of laser ignition. It is shown that many features of laser ignition can be understood on the basis of simple thermal concepts, particularly when the effects of thermal or radical losses are considered. It is proposed that the main advantages of laser sources are likely to be in the timing and placement of ignition rather than the inherent energy requirements. Potential applications to combustion systems of practical importance, e.g., high-speed propulsion systems, are discussed and instructive laboratory-scale experiments are suggested.