The purpose of this study was to test the reliability and validity of an acanthosis nigricans (AN) screening tool for use in elementary school-age children of different ethnic groups. Cross-sectional data were collected via observation of 288, 5- to 12-year-old school-age children. Three nurse clinicians used a 0-4 grade AN screening tool to rate each child's level of AN independently. AN was consistently and appropriately identified in elementary school-age children from different ethnic groups. All clinicians were within one grade 98% of the time. Substantial agreement among raters was found (kappa statistic = 0.822, p [less than or equal to] 0.001), indicating similar interpretation and reproducibility of the AN screening tool. There was more consistent detection of grade four AN regardless of the children's sex, body mass index, or ethnic group. The AN screening tool is easy to use and reliable for use with elementary school-age children of various ethnic groups. (Contains 2 tables and 2 figures.)