OBJECTIVES The Balance Error Scoring System (BESS) is a commonly used test in adolescents and young adults. Affordability and portability of newer force plates has led to instrumentation of many clinical balance tests including the BESS. Despite the higher precision of force plate measures compared with clinical scoring, it is unclear if the instrumented BESS demonstrate concurrent validity and reliability when compared with the original BESS. The purpose of this study was to examine the reliability and concurrent validity of instrumented BESS testing using a commercially available force plate system. METHODS Thirty-six participants participated in the initial testing day (17 male/19 female, M = 15.9 years, SD = 1.5 years). The test-retest sample consisted of 26 participants who completed the same testing procedure after 1 week. For all testing sessions, participants performed the BESS while standing on a portable force plate system. Number of errors and sway velocity were obtained. Concurrent validity was established through correlation analysis examining the relationship between the original and the instrumented BESS scores. Reliability was established using Intraclass Correlation Coefficient (ICC3,1) computed for the instrumented and the original BESS. RESULTS A significant moderate relationship exists between the total scores of the original and the instrumented BESS (rs = 0.54, p = 0.001). Despite a range of reliability scores for the different conditions in the instrumented BESS (ICC3,1 = 0.19-0.61) and the clinically scored BESS (ICC3,1 = 0.13-0.71), the reliability score for the total test score was the same for the instrumented and the clinical test (ICC3,1 = 0.74). CONCLUSION Although the instrumented BESS may appear to demonstrate concurrent validity against the original BESS, instrumentation did not improve its reliability. Future research should examine if the instrumented BESS demonstrates validity against laboratory level force plates and if it is able to overcome the ceiling effect reported for the clinical BESS test.