This paper describes our recent progress in the realization of all-optical logic devices using integrated waveguides in a III-V semiconductor. The potential for high speed all-optical signal processing is discussed. The physical mechanisms for the optical nonlinearity, including the important role of waveguide heating, are considered for their influence on device design. The measurement of the nonlinearity in several III-V's making use of a wave-guide Fabry-Perot interferometer is presented. A preliminary device based on a Mach-Zehnder waveguide interferometer has been fabricated in GaAs.