A study analyzed the effects of classwide peer tutoring on science vocabulary spelling achievement for three language groups in one school's sixth grade. The groups consisted of: (1) Spanish-dominant and limited-English-proficient (LEP) students (n=8); (2) students proficient at grade level in both Spanish and English (n=14); and (3) monolingual English speakers (n=5). For comparison of weekly spelling gains, the second and third groups were combined as one non-LEP group. Experimental stimuli were drawn from the sixth-grade science text. Results of weekly spelling pre- and post-tests demonstrated that the peer tutoring procedures resulted in gain scores for the three language groups. In addition, the Spanish-dominant LEP group made greater gains when compared to the non-LEP group. Implications for the design and implementation of peer tutoring programs for LEP students are discussed. An 11-item bibliography is included. (Author/MSE)