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This paper discusses the desiqn and realization of amethod of lexical retrieval which has been incorporated intothe &BN; speech understanding system. As a component of thissystem, Lexical Retrieval operates on a phonetic segmentlattice whose segments re described probabilistically. Itsfunction is to return an ordered list of the most probablewords and their location within the lattice. The wordsconsidered in any such scan can be constrained as to class,location, and phonetic context. This method of lexicalretrieval takes advantage of a representation ofphonological word boundary rules which enables theireffective use, independent of whether the phonetic contextis unknown as in word spotting, or known, as in a scan tothe left or right of a previously located word. Thisability to take account of word boundary effects in a cleanand efficient way is one of the major accomplishments ofthis work.