OBJECTIVE To assess intraobserver repeatability and interobserver and in vivo versus photographic agreement of a scoring system for the implant-skin interface (ISI) of external skeletal fixation (ESF). SAMPLE 42 photographs of ISIs from 18 dogs for interobserver agreement and intraobserver repeatability and 27 photographs of ISIs from 6 dogs for in vivo versus photograph agreement. PROCEDURES An ISI inflammation scoring system was developed. It included scales for 6 metrics (erythema, drainage amount, drainage type, swelling, hair loss or lack of hair regrowth, and granulation tissue). Photographs of the ISI of ESF were obtained by use of a standard protocol and evaluated to determine intraobserver repeatability and interobserver agreement (Cronbach α; 4 raters) of the ISI score. Agreement between in vivo and photographic ISI scores (2 raters) and correlation between median scores across metrics were evaluated. RESULTS 42 photographs met the inclusion criteria. Overall intraclass correlation coefficients ranged from 0.922 to 0.975. Interobserver overall Cronbach α ranged from 0.835 to 0.943. For in vivo versus photographic assessment, 27 ISIs in 6 dogs and their photographs were evaluated. The Cronbach α for both raters ranged from 0.614 to 0.938. Overall, the Cronbach α ranged from 0.725 to 0.932. Mean photographic scores were greater than mean in vivo scores for each metric. Pearson correlation coefficients ranged from 0.221 to 0.923. Erythema, swelling, and granulation were correlated with all other metrics. CONCLUSIONS AND CLINICAL RELEVANCE In this study, an ISI scoring system used in this study had high repeatability and agreement and may therefore be considered for use in clinical situations. Photographic scores were not equivalent to in vivo scores and should not be used interchangeably.