This study examined the methods reportedly used to identify reinforcers in 97 skill acquisition studies involving people with autism published from 2005 through 2009. Results indicated that 32 of the 97 studies (33%) provided such information. Interviews with persons familiar with participants (e.g., parents, teachers) were the most-used techniques, followed in order by asking participants what they preferred, observing participants in their natural environment, and conducting formal preference assessments. Although effective reinforcers appear to have been used in each of the studies, the failure of many articles to describe how those stimuli were identified may make it difficult for practitioners and researchers to replicate the interventions. Future publications would benefit from the inclusion of clear and detailed specifications of the procedures used to isolate reinforcers. (Contains 3 tables.)