Two cases of guttural pouch mycosis in race horses were observed for clinical and pathological aspects of the disease to investigate etiology and pathogenesis of dysphagia and epistaxis of the horse. In case 1 showing prolonged dysphagic sign a diphtheritic membrane was confined to the guttural pouch involved with neuritis of the glossopharyngeal nerve due to fungal penetration. The other horse showing fatal recurrent epistaxis had lesion of mycetoma invading the internal carotid artery to provoke erosion of the artery. An Aspergillosis sp. was isolated from the guttural pouches of the two horses and identified as A nidulans.