The use of marginal reading glosses by 18 second language (L2) learners is examined through a quantitative and qualitative analysis of audiotaped think-aloud protocols. How these readers interact with the glosses is identified and divided into five categories or gloss interactions. Examples from each are presented. The primary research question investigated is the following: In print medium, how do intermediate-level readers of L2 Spanish interact with and apply marginal glosses? More specifically, as identified through think-aloud oral expression, how is readers' comprehension positively or negatively influenced by marginal gloss use? Findings reveal that although the participants used the glosses to facilitate comprehension 54% of the time, unanticipated uses are also identifiable. Included are examples and suggestions for promoting reading comprehension through marginal gloss use.