Objectives To adapt the trunk stability test to facilitate the further sub-classification of higher levels of core stability in athletes for use as a screening tool. To establish the inter-tester and intra-tester reliability of this adapted core stability test. Design Reliability study; Setting Collegiate athletic therapy facilities. Participants Fifteen physically active male subjects (19.46±0.63) free from any orthopaedic or neurological disorders were recruited from a convenience sample of collegiate students. Main Outcome Measures The intraclass correlation coefficients (ICC) and 95% Confidence Intervals (CI) were computed to establish inter-tester and intra-tester reliability. Results Excellent ICC values were observed in the adapted core stability test for inter-tester reliability (0.97) and good to excellent intra-tester reliability (0.73-0.90). While the 95% CI were narrow for inter-tester reliability, Tester A and C 95% CI’s were widely distributed compared to Tester B. Conclusions The adapted core stability test developed in this study is a quick and simple field based test to administer that can further subdivide athletes with high levels of core stability. The test demonstrated high inter-tester and intra-tester reliability.