A review of the application of acoustic emission (microseismic) techniques to the geotechnical area will be given. The approach will be somewhat historical starting with the pioneering work (in the 1930's) by Obert and Duvall in the coal and metal mines and continuing up to the present where currently a host of materials and engineering problems are being investigated with acoustic emission techniques. Acoustic emission measurements in the laboratory will be described which have given insight into the mechanical behavior of rocks, soils, coal and ice. Field applications which will be dealt with include determination of the stability of mine tunnels, open pit mine slopes, underground gas storage reservoirs, and earthem dikes and dams. The use of acoustic emission techniques in earthquake prediction studies will be reviewed. [The authors' work has been supported by EPA.]