Six horses from several geographical locations in New Zealand presented with signs of guttural pouch mycosis. All horses had experienced epistaxis within 14 days of presentation. In five horses with epistaxis, a diagnosis of guttural pouch mycosis was made on endoscopic observation of fungal plaques in the affected guttural pouches. One of these cases died before surgery was attempted. The remaining four cases underwent ligation and balloon catheter occlusion of the internal carotid artery of the affected pouch. Three of these horses survived and were reported to be healthy 1 year after surgery. One case died from haemorrhage 8 weeks after surgery. In a sixth horse, endoscopy was carried out but the affected guttural pouch which had recently haemorrhaged was not entered. This horse underwent ligation of the internal carotid and occipital arteries of the affected side but subsequently died. A diagnosis of guttural pouch mycosis of the maxillary artery was confirmed by post-mortem examination. Histology revealed fungal hyphae within thrombi in the lumen of the maxillary artery in the affected guttural pouch. Two horses displayed signs consistent with cranial nerve damage in the guttural pouch. Guttural pouch mycosis. This is the first report of which we are aware of the diagnosis and treatment of clinical cases of guttural pouch mycosis in horses in New Zealand. Practitioners in New Zealand should be aware of the presence and manifestations of this disease and be prepared to treat or refer horses for surgical treatment before fatal haemorrhage and/or profound neurologic signs occur.