Highly preferred stimuli were identified via two preference assessments (based on Fisher et al., 1992), the second of which included stimuli that were ranked low in the initial preference assessment. Following the preference assessments, a subset of stimuli was evaluated as reinforcers in single- and concurrent-operant arrangements. In general, stimuli that were identified as highly preferred in the initial preference assessment functioned as more effective reinforcers. These results are discussed in terms of how the context in which stimuli are evaluated may play a role in the identification of effective positive reinforcers for individuals with autism and related developmental disabilities. (Contains 3 figures.)