Content-based language instruction has become a widely adopted pedagogical approach to EAP. This paper reports the results of a study of the effects of content-based ESL instruction on students' future academic performance. The study used college academic records to evaluate the academic performance of two groups of ESL students who enrolled as first semester freshmen from Spring 1995 to Spring 2000. Students simultaneously enrolled in a content-linked ESL program were compared to students who did not receive content-based ESL instruction. The study found that students enrolled in the content-linked ESL program not only achieved higher pass rates and better grades in the ESL course, but also performed better in subsequent ESL and developmental English courses. In addition, the content-linked ESL students had better long-term academic success rates than non-content-linked ESL students did, in measures such as English proficiency test pass rates, graduation and retention rates, and overall GPA.