Minimal evidence exists regarding the retrospective pretest's effectiveness as a tool to obtain usable, indirect evidence of student learning in open admissions institutions. The researcher conducted this study to determine if a retrospective pretest more accurately detected a change in students' knowledge compared to a conventional pretest-posttest. The researcher designed a 17-item inventory covering course objectives, and students were randomly assigned to either a retrospective pretest (referred to as post-then) or a conventional pretest-posttest group. Findings indicated that participants in the post-then group reported a greater change in knowledge compared to the conventional group. This finding supported the use of the retrospective pretest as a tool for getting usable, indirect evidence of student learning. Future research needs to examine response effect, alternative ways of calculating treatment effect and the confounding influences of other perceptual variables. (Contains 2 tables and 3 figures.)