We evaluated behavior exhibited by individuals with developmental disabilities using progressive-ratio (PR) schedules. High- and low-preference stimuli were determined based on the results of a paired-stimulus preference assessment and were evaluated in subsequent reinforcer and PR assessments using concurrent and single schedules of presentation. In Experiment 1, results showed that for 2 of 3 participants, stimuli determined to be low-preference functioned as reinforcers when evaluated independent of high-preference stimuli. Further, the results from Experiment 2 showed that low-preference stimuli also functioned as reinforcers under gradually increasing PR requirements. Results suggest that for cases in which a high-preference stimulus is unavailable or impractical, the contingent delivery of relatively less preferred stimuli may maintain appropriate behavior, even as schedule requirements increase.