this study investigated the effects of three kinds of gloss conditions, that is traditional non-call marginal gloss, audio gloss, and extended audio gloss, on reading comprehension and vocabulary gain of iranian upper- intermediate efl learners. to this end, three experimental and one control groups, each comprising 15 participants, took part in the current study. in order to ensure that the participants were from the right proficiency level, ket (key language test) was used to select upper-intermediate proficiency learners. participants in each group read two passages under one of the three mentioned conditions, with no gloss offered for control group. they all completed one pre-test, one reading session, one post-test, and one delayed pos-test of reading and vocabulary for each text. the data were analyzed using t-tests and one-way anovas for both vocabulary and text comprehension for both immediate and delayed post-tests. statistical analyses of the results revealed that extended audio gloss group, who were provided with the voice of a speaker to read the meaning of the target word, as well as one example sentence, significantly outperformed the other groups in terms of reading. regarding vocabulary learning, the audio and extended audio gloss groups both outperformed the other groups. further results and implications are discussed in the thesis.