Both classroom instruction and lexical database development stand to benefit from applied research on sign language, which takes into consideration American Sign Language rules, pedagogical issues, and teacher characteristics. In this study of technical science signs, teachers' experience with signing and, especially, knowledge of content, were found to be essential for the identification of signs appropriate for instruction. The results of this study also indicate a need for a systematic approach to examine both sign selection and its impact on learning by deaf students. Recommendations are made for the development of lexical databases and areas of research for optimizing the use of sign language in instruction.