Gordon B. Willis is a cognitive psychologist in the Applied Research Program, National Cancer Institute, National Institutes of Health; and lectures for the Joint Program for Survey Methodology (JPSM). Prior to that, he was a research methodologist at Research Triangle Institutes in Rockville, Maryland, where he established a cognitive laboratory facility. He also worked for over a decade in the Questionnaire Design Research Laboratory at the National Center for Health Statistics, CDC, developing and applying cognitive interviewing techniques. Dr. Willis attended Oberlin College, and received a Ph.D. in cognitive psychology from Northwestern University. He now works mainly on the development and evaluation of questionnaires that collect information on cancer risk factors. His main research interest is the evaluation of survey pretesting techniques, especially the cognitive interview. Dr. Willis is an authority on the use of cognitive interviewing, based on his work on developing and practicing these methods at three different organizations. He has personally conducted hundreds of cognitiv interviews and overseen the work of teams of interviewers. He has taught cognitive interviewing in short courses at survey conferences and in university lectures. Willis has also written extensively on the practice and theoretical and empirical evaluation of cognitive interviewing techniques.