A study examined the effects of the use of sign language in young hearing children's language development. The study tracked a class of 19 Maryland students from their first week of prekindergarten over the 2-year period that ended with the last week of their kindergarten year. Subjects received sign instruction during the prekindergarten year and none in the kindergarten year and were tested at the end of the kindergarten year. The testing instrument was the Peabody Picture Vocabulary Test (PPVT-R), which showed students receiving sign language instruction scored significantly higher than similar students in comparable classes not receiving such instruction. Results indicated that the gain subjects achieved during their sign-language-enhanced prekindergarten year continued throughout their kindergarten year, with test results confirming that there was no memory decay over time. Findings suggest that the addition of sign language in their prekindergarten curriculum made a significant increase in these students' vocabularies and was sustained in the absence of any further sign instruction in their kindergarten program. Further study of the effect of sign language instruction on hearing children's language development is needed concerning the specific reason additional linguistic modalities interact in such a positive way with language growth. (Contains 28 references.) (CR)