Background: Although nutritional screening with a tool such as the Malnutrition Universal Screening Tool (MUST) is recommended for outpatients, staff are under pressure to undertake a variety of other tasks. Little attention has been paid to the validity of patient self-screening with MUST.Objective: This study in 205 outpatients with a mean (6SD) age of 55 6 17 y (56% male) assessed the practicalities of self-screening, its agreement with screening undertaken by a trained health care professional (HCP), and its test-retest reliability. Design: After the participants provided consent, screening was undertaken by the patients themselves and then by a trained HCP who was unaware of the self-screening results. All patients completed an ease-of-use questionnaire. Test-retest reliability of self-screening was established in a subset of 60 patients. Results: A total of 19.6% of patients categorized themselves as "at risk" of malnutrition (9.8% medium, 9.8% high). For the 3-category classification of MUST (low, medium, high), agreement between self-screening and HCP screening was 90% (k = 0.70; SE = 0.058, P , 0.001). For the 2-category classification (low risk, medium + high risk), agreement was 93% (k = 0.78, SE = 0.057, P , 0.001). Disagreements were not systematically under-or overcategorized. Test-retest reliability was almost perfect (k = 0.94, P , 0.001). Most patients (71%) completed self-screening in ,5 min. Patients found the tool easy or very easy to understand (96%) and complete (98%), with 94% reporting that they were happy to screen themselves. Conclusion: Self-screening involving MUST in outpatients is acceptable to patients, user-friendly, reliable, and associated with good agreement with HCP screening. This trial was registered at clinicaltrials.gov as NCT00714324.Am J Clin Nutr 2012;96: