['To determine the reliability and validity of scales measuring low-fat milk consumption self-efficacy and norms during school lunch among a cohort of 5th graders.', 'Two hundred and seventy-five students completed lunch food records and a psychosocial questionnaire measuring self-efficacy and norms for school lunch low-fat milk consumption during the fall and spring semesters of the 1998-1999 academic year. Test-retest reliability was assessed in participants who also completed the questionnaire in the spring semester (n = 262). Principal component analyses identified and confirmatory factor analyses confirmed latent variables. Bivariate correlations measured construct validity.', 'Houston-area middle school.', 'Fifth graders (n = 275) from one middle school in southeast Texas.', 'Two scales measuring psychosocial influences of low-fat milk consumption were identified and proved reliable in this population: milk self-efficacy and milk norms. Milk self-efficacy and norms were positively correlated with milk consumption and negatively correlated with consumption of sweetened beverages.'] Are measures of self-efficacy and norms for low-fat milk consumption reliable and related to beverage consumption among 5th graders at school lunch?