A weanling Thoroughbred foal was admitted to Equine Hospital, Korea Racing Association with signs of colic. On admission the foal was sweating profusely, appeared anxious and exhibiting signs suggestive of abdominal pain. Clinical examination revealed: tachycardia (90 beats/min), tachypnea (50 breaths/min) and congested and slightly cyanotic mucous membranes. No intestinal sounds were auscultated in all 4 abdominal quadrants. Rectal palpation identified concurrent cecum and large colon impactions. Treatment consisted of intravenous administration of a balanced electrolyte solution, nasogastric siphonage and administration of analgesics. Nasogastric reflux contained ascarids. This treatment failed to alleviate the signs of colic. The foal died 3 hours later following discharge because the owner didn't want laparatomy because of economic constraints. Prior to admission this foal had not received any prophylactic anthelmintic treatment. In necropsy, there were masses of ascarids accumulation in the stomach, small intestine and large intestine. The outcome of this report is to describe the first diagnosed case of gastrointestinal impaction by P. equorum in a Thoroughbred foal in South Korea and indicates the importance of regular anthelmintic treatment.