The present study investigated the role of phonological and orthographic processing skills in adult second language reading. The subjects were 60 ESL graduate students; all were native speakers of Farsi. Three types of ESL reading measures were used as criterion variables: reading comprehension, silent reading rate, and the ability to recognize individual words. Data were analyzed using correlational and hierarchical multiple regression. Efficiency in phonological and orthographic processing contributed significantly to individual differences on the reading measures. In particular, efficiency in orthographic processing contributed to the reading measures independently of syntactic and semantic measures. The study suggests that it is useful to consider individual differences in ESL reading with respect to individual differences in lower level processes – particularly the efficiency with which readers process phonological and orthographic information.