Reading in a second language (L2) is not a monolingual event; L2 readers have access to their first language (L1) as they read, and many use it as a strategy to help comprehend an L2 text. Owing to difficulties in observing the comprehension process, little research has been conducted to determine what role the L1 plays in the reading strategies of L2 readers. Using think-aloud protocols and retrospective interviews with 20 native speakers of Chinese and Japanese at three levels of language proficiency studying in the United States, this study explores further the question of when L2 readers use their L1 cognitive resources and how this cognitive use of the L1 helps them comprehend an L2 text. We conclude by suggesting that the results support a sociocultural view of the L2 reading process.