Three horses were referred for investigation of a unilateral foul smelling scanty nasal discharge, complicated in one case by intermittent epistaxis. Thick purulent material or a mycotic plaque was identified by an endoscopic examination of the middle meatus but in two horses this had to be repeated under general anaesthesia before the abnormalities were detected. Aspergillus fumigatus was cultured from all three cases and septate hyphae were identified on smears from lesions. Histological examination of the lesion in one case revealed a fungal mycelium. Topical treatment with natamycin solution in all cases plus nystatin in two of the horses resulted in complete recovery from the condition in two cases but in one case the problem recurred. The aetiology of nasal aspergillosis remains uncertain.