The overall prevalence of gastric ulcers was 70.9 % , with a median ulcer score of 3.0 (range: 2–5). Most ulcers were present on the squamous portion of the stomach, while two mares had glandular ulcers. There were no differences in the presence, location and severity of gastric ulcers between pregnant and non-pregnant mares. Furthermore, there were no significant associations between the variables measured and the presence of gastric ulceration. The prevalence of gastric ulceration in this specific population of horses was higher than expected and further investigation is warranted to determine the factors that contributed to this finding.