This paper presents a new method for utilizing translator knowledge bases for machine translation systems. Translator knowledge to be stored and utilized consists of ‘translationally equivalent pattern pairs’: surface-level phrasal, clausal, and sentential correspondences between the source and target languages. This knowledge will be utilized to translate domain-specific idiomatic, nonstandard, or ungrammatical expressions. The proposed method has been implemented in an adaptive English to Japanese machine translation system, HICATS/EJ, as one of its customization facilities.