The purpose of the study was to find the source of complaints and to diagnose dynamic upper respiratory tract problems, which were derived from the horse owners, trainers, and jockeys, and to evaluate the overground endoscopic examination efficiency to determine the subclinical upper respiratory tract (URT) abnormalities, which were unable to diagnose with resting endoscopy. In the study, overground endoscopy has been used which nowadays there is a more useful and safe technique of performing endoscopy during ridden exercise in the natural field to diagnose dynamic upper respiratory tract (URT) abnormalities in comparison with the more traditional method of resting endoscopy. This study focused on 25 racehorses (Thoroughbred, n:22 and Arabian n: 3), which were admitted to Racehorse Hospital with complaints of fade abruptly and/or abnormal respiratory noise during the last meters of the race. All horses were examined for the complaints to be associated with systemic disorders and/or lameness, the racehorses with lameness and/or systemic disorders findings were excluded. Resting (post-exercise) and overground endoscopy by using Dr. Fritz® ETL-Equine Overground Endoscopy was performed on a polytrack racecourse in all racehorses. Observed abnormalities were recorded as simple and complex cases and the results of resting and dynamic examination were compared. It was concluded the overground endoscopic examination has a useful diagnostic value in determining the cause of abnormal respiratory noise and/or fade abruptly.