In recent years there has been a growing interest to incorporate hypertext glosses into L2 reading materials and accordingly, it has provoked researchers to uncover to what extent and under what contextual factors, a specific type of gloss yield more effective outcomes than other types of glossing. To quantitatively synthesize the results obtained from the numerous studies that had been conducted in this area, the present meta-analysis was conducted attempting to examine the magnitude of the effect of different gloss types (single vs. multiple glosses) on L2 vocabulary acquisition along with identification of the contextual factors that influence between-study variation through synthetizing 34 primary articles satisfied the inclusion criteria. The overall mean effect size was found to be + 0.83 (p<0.05), indicating that multiple glosses (text+visual) had a large, positive effect on learners' vocabulary acquisition than single mode of glossing (text-only). Moderator analyses further suggested that intensity of the program and L2 proficiency level were potential moderators influencing the heterogeneity between effect sizes, whereas the learning context, sample size and research design did not have such impact. Such a meta-analytic review will undoubtedly provide a map of the past and current researches in the field of computer technology and language education, showing the pathway for future studies. Moreover, unlike individual studies which present solely the results of the test of significance, meta-analytic reviews show the magnitude of effect size, shedding light on the nature of the relationships between variables.

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