The purpose of this study was to determine the effect of simplification and elaboration, as two types of input modification, on reading comprehension and reading strategy use of expository text of Iranian EFL learners. Ninety five learners of English who formed three groups of simplification, elaboration and control, participated in the study. An oxford placement test (OPT) was used to homogenize the learners based on their general proficiency. Reading comprehension of the learners was assessed using a researcher-made reading test and reading strategy use of the learners was checked through a reading strategy questionnaire adapted from Phakiti (2006). The two experimental groups, simplification and elaboration, studied the texts which were modified. Following Oh's (2001) strategies, the researcher added redundancy and clearer signaling of thematic structure in the form of example, paraphrase and repetition of original information, and synonyms to elaborate the expository texts. And again following Oh's (2001) strategies, to make texts simplified the researcher decreased the length of the sentences and the number of embedded clauses as well as the number of multisyllabic and low-frequency words. The control group worked with the expository texts without any simplification and elaboration. It is also worth-mentioning that the participants in all three groups studied five expository text structures (listing, comparison / contrast, temporal sequence, cause / effect, and problem/solution). Results obtained from the one-way ANOVA analyses revealed that both simplified and elaborated input increased reading comprehension of the EFL learners as the participants in these groups outperformed the learners in control group. However, the analyses of the reading strategy use of the learners showed that just the elaborated group performed better than the other two groups. The findings suggests that input modification may be a useful technique for reading comprehension, and elabora
