BACKGROUND AND OBJECTIVES: Web-based cases are well accepted by medical students and enable faculty to deliver equivalent educational experiences to all students. A 2009 literature search revealed no study investigating student use patterns of Web-based case libraries for self-directed learning. We investigated third-year students' use of a Web-based case program for self-directed learning in a family medicine clerkship. METHODS: We analyzed Design A Case usage patterns of 210 medical students during academic year 2008--2009. We compared board score differences between these students and those from the previous 5 years who did not use Design A Case. We analyzed data from a 13-item survey, administered to a subgroup of 85 students, about the strengths, weaknesses, and acceptability of the program. RESULTS: Students completed, on average, four cases, which was beyond the requirement of three. They reported that the content was highly relevant to cases they saw in clinic. Almost 75% preferred the self-directed Web-based learning over didactics, and most (64%) felt they learned more electronically. Use of the cases was associated with equivalent Board scores versus didactic lectures. CONCLUSIONS: In our setting, self-directed learning using a Web-based case program was highly acceptable to students. Web-based cases may provide an option for family medicine educators who wish to deliver equivalent educational experiences across sites