Although much research on English for specific purposes (ESP) has been conducted, little focus has been placed on investigating the mechanisms involved in ESP readers' comprehension process. This case study explored the reading process that characterizes a competent ESP reader's comprehension. A juris doctor student attending a major university in the United States was selected for the case study. Qualitative data were gathered through a semi-structured interview, recall protocol, and document analysis, and were thematically coded. The findings revealed the following: (a) The professional domain determines the major purposes of ESP reading. (b) Institutional demands and inadequate L2 proficiency within the target discourse prevent background knowledge in the first language (L1) from being transferred to L2 texts are the major sources of comprehension difficulty. (c) Three strategies can be used to overcome such difficulties. First, schemata (background knowledge) in L1 can facilitate comprehension and enhance the reading process. Second, genre knowledge learned in L1 can be used to dissect the information structure of L2 texts. Finally, the use of L1-based materials can help to overcome the comprehension difficulties arising from the L2 material. The implications for L2 reading instruction and future ESP reading research are discussed.