Language learners have unprecedented opportunities for developing second language literacy skills and intercultural understanding by reading authentic texts on the Internet and in multimedia computer-assisted language learning environments. This article presents findings from a meta-analysis of 11 studies of computer-mediated glosses in second language reading comprehension and incidental vocabulary learning. Computer-mediated glosses had an overall medium effect on second language reading comprehension and a large effect on incidental vocabulary learning. Mean effect sizes varied from medium to large depending upon the level of instruction, text type, and assessment tasks. Drawing upon findings of this meta-analysis and the overall characteristics of gloss studies, we propose recommendations for future research, including replications and the systematic study of reading variables and learner individual differences in multimedia learning environments with authentic texts. (Eight appendixes include: (1) Definitions of selected study characteristics; (2) Coding book; (3) Study characteristics, phase one; (4) Study characteristics, phase two; (5) Exclusion criteria; (6) Coding reliability of categories; (7) Selected study characteristics and effect sizes for L-2 reading comprehension; and (8) Selected study characteristics and effect sizes for L-2 vocabulary learning. Contains 7 tables and 4 notes.)