abstract poor reading comprehension can result in failure in using references, benefiting from professional gatherings and resources, keeping up with the growing body of knowledge in the virtual world of the internet, and failing to achieve in efl programs. the purpose of the present quasi-experimental study was to explore the effects of background knowledge and previewing narrative and expository texts on the reading comprehension of a group of iranian university efl learners. participants were 82 efl learners enrolled in 4 intact classes at the english department of university of kashan. each class was a treatment group and read the same four texts, two narrative short stories and two expository texts. the conditions of the performance of the reading comprehension tasks were, however, experimentally manipulated for these groups to explore the effects of previewing and background knowledge alone or in combination. the participants’ initial reading ability was also measured through a version of the ielts test. one group listened to a brief presentation of background knowledge, another to a preview presentation/read previews, a third to a combination of both before task performance. the forth group read the texts without any assistance or experimental interference. multiple comparisons between groups indicated that there was a statistically significant difference between the type of the text and the preview (preview vs. no preview) and background knowledge (background knowledge vs. no background knowledge). the students received significantly higher reading comprehension scores when they were provided with both preview and background knowledge before reading the narrative texts. the results are discussed in terms of the facilitative effects of preview and background knowledge on efl learners’ reading comprehension. practical implications for efl reading instructors are discussed as well.