Gastric ulceration is a common condition of both foals and horses. The prevalence of gastric ulcers in foals has been reported to be as high as 25% to 50%, depending upon the age of the foal and other contributing factors. Surveys of yearling and adult horses have shown that gastric ulceration is common in older horses as well with a prevalence of between 52% of apparently normal horses and up to 100% of horses with poor appetite, poor body condition or abdominal discomfort. Performance horses in training have been shown to be at increased risk of gastric ulceration. Diagnosis of gastric ulcers is made by the presence of clinical signs, endoscopic findings and response to treatment. Testing for fecal occult blood is only helpful in young foals and contrast radiography can be unreliable. Gastroendoscopic examination is the "gold standard" for diagnosis of gastric ulceration in the horse.