Objective: To compare Orchard Sports Injury Classification System (OSICS-10) sports medicine diagnoses assigned by a clinical and non-clinical coder. Design: Assessment of intercoder agreement. Setting: Community Australian football. Participants: 1082 standardised injury surveillance records. Main outcome measurements: Direct comparison of the four-character hierarchical OSICS-10 codes assigned by two independent coders (a sports physician and an epidemiologist). Adjudication by a third coder (biomechanist). Results: The coders agreed on the first character 95 of the time and on the first two characters 86 of the time. They assigned the same four-digit OSICS-10 code for only 46 of the 1082 injuries. The majority of disagreements occurred for the third character; 85 were because one coder assigned a non-specific X code. The sports physician code was deemed correct in 53 of cases and the epidemiologist in 44 . Reasons for disagreement included the physician not using all of the collected information and the epidemiologist lacking specific anatomical knowledge. Conclusions: Sports injury research requires accurate identification and classification of specific injuries and this study found an overall high level of agreement in coding according to OSICS-10. The fact that the majority of the disagreements occurred for the third OSICS character highlights the fact that increasing complexity and diagnostic specificity in injury coding can result in a loss of reliability and demands a high level of anatomical knowledge. Injury report form details need to reflect this level of complexity and data management teams need to include a broad range of expertise.