This book presents a detailed description of Spoken Language Translator (SLT), one of the first major projects in the area of automatic speech translation. The SLT system can translate between English, French, and Swedish in the domain of air travel planning, using a vocabulary of about 1,500 words, and with an accuracy of about 75 percent. The greater part of the book describes the language processing components, which are largely built on top of the SRI Core Language Engine, using a combination of general grammars and techniques that allow them to be rapidly customized to specific domains. Speech recognition is based on Hidden Markov Mode technology, and uses versions of the SRI DECIPHER system.