Research has suggested that a daily multiple-stimulus-without-replacement (MSWO) preference assessment may be more sensitive to changes in preference than other assessment formats, thereby resulting in greater correspondence with reinforcer efficacy over time (DeLeon et al., 2001). However, most prior studies have measured reinforcer efficacy using rate of responding under single-operant arrangements and dense schedules or under concurrent-operants arrangements. An alternative measure of reinforcer efficacy involves the evaluation of responding under progressive-ratio (PR) schedules. In the present study, 7 participants were given a single paired-stimulus (PS) preference assessment followed by daily MSWO preference assessments. After each daily MSWO, participants responded for each stimulus on a PR schedule. The correspondence between break points and preferences, as assessed by the 2 assessment formats, was examined. Results demonstrated that both preference assessments did equally well at predicting reinforcer efficacy, although the PS more consistently identified the most effective reinforcer. (Contains 3 figures and 1 table.)