English as a second language (ESL) teachers have long noted that native speakers of Arabic exhibit exceptional difficulty with English reading comprehension (e.g., Thompson-Panos & Thomas-Ruzic, 1983). Most existing work in this area has looked to higher level aspects of reading such as familiarity with discourse structure and cultural knowledge to explain native Arabic speakers' ESL reading difficulties (Abu Rabia, 1996). However, higher level processes often depend on lower level processes, such as letter and word identification, and deficient lower level processing can inhibit reading comprehension (Koda, 1990). Given important differences in the written representation of vowel information in English and Arabic writing, it was hypothesized that the English reading comprehension difficulties experienced by Arabic speakers might also reflect nontarget-like lower level processing of letters and words. Two experiments compare the reading processes of native Arabic speakers to the reading processes of native English speakers and non-Arabic ESL learners and provide some evidence that native Arabic speakers are less aware of vowel letters in English texts than either control group. This differential awareness of vowel letters may contribute to native Arabic speakers' ESL reading comprehension difficulties. The implications of this research for ESL pedagogy are discussed. (Contains 4 tables, 2 figures, and 3 footnotes.)