The subject of electromagnetically induced transparency (EIT) is reviewed in this paper. Emphasis is placed on the experimental work reported in this field since 1990. Theoretical work is also covered, although it is not intended to review all the very numerous recent theoretical treatments on this topic. The basic physical ideas behind EIT are elucidated. The relation of EIT to other processes involving laser-induced atomic coherence, such as coherent population trapping, coherent adiabatic population transfer and lasing without inversion, is discussed. Experimental work is described covering the following topics: EIT with pulsed and continuous-wave sources, lasing without inversion, pulse propagation in a laser dressed medium and EIT in nonlinear optical processes. A full set of references and a bibliography are included.