Brief screening instruments can roughly characterize individual behavior and target those most in need of change. However, the level of agreement between abbreviated and full-scale instruments is often unknown. We determined agreement between a brief screener and an in-depth survey for assessing eligibility into a randomized controlled trial to improve lifestyle behaviors among cancer survivors who consumed diets with >or=30% total energy from fat or fewer than five servings of fruits and vegetables per day, and/or who exercised <150 min/wk. Responses of 203 subjects to mailed screeners, which included scales from the National Cancer Institute (NCI)Percent Energy from Fat Screener and 5-A-Day trials, and one item on exercise, were compared with data from telephone interviews using the Diet History Questionnaire and the 7-Day Physical Activity Recall. Moderate correlations and fair agreement existed between screener and survey for intakes of fat [ r =0.54 ( P <.0001)/kappa statistic (ks)=0.35] and fruits and vegetables [ r =0.50 ( P <.0001)/ks=0.32], whereas agreement was low for exercise (ks=0.15). NCI and 5-A-Day screening instruments perform relatively well in targeting cancer survivors most in need of dietary change. Decisions to use brief screening instruments should be based on available resources and tolerance for misclassification.