¹Istanbul Pendik Veterinary Control Institute, Department of Pharmacology, Doping Control Laboratory, TR-34890 Istanbul - TÜRKIYE DOI : 10.9775/kvfd.2025.35607 The use of prohibited substances raises significant ethical and global issues for horseracing. To mitigate these problems and maintain control, prohibited substance controls are conducted on samples taken from thoroughbred horses before and after races. However, limited information is available on prohibited substances detected as a result of these controls. In this study, 39.935 samples from races held at three racetracks in Türkiye between 2015 and 2023 were analysed qualitatively and/or quantitatively using gas chromatography-mass spectrometry, liquid chromatography-mass spectrometry, high-resolution mass spectrometry, inductively coupled plasma mass spectrometry, and a biochemistry autoanalyser. Overall, 219 violations caused by 314 findings were reported. Of these findings, 140 were International Screening Limit, 86 were prohibited for use at any time, 60 were threshold, and 28 were substances within the scope of International Residue Limit. Consequently, violations detected at three major racetracks in Türkiye over nine years were evaluated, and useful information was shared with scientists working in this field, race veterinarians, horse owners, and trainers. Keywords : Horseracing, anti-doping, Türkiye, prohibited substance, racetracks