A case of chromoblastomycosis confined to the mucous membrane of one side of the nasal septum is reported. The organism was not cultivated, but its characteristics in histological preparations were typical of those of the organisms in sections of cutaneous lesions known to be caused by Phialophora pedrosoi and related fungi. The diagnosis is considered to have been justified in spite of the great rarity of mucosal involvement in chromoblastomycosis and of the complete absence of lesions in the skin. The patient was a Sinhalese student working in London. He had first noticed the lesion before he left Ceylon, but the symptoms of nasal obstruction and bleeding were not sufficient to make him seek medical advice until two years later. If it is correct to assume that he contracted the infection in Ceylon his case is only the second on record in which there has been reason to suggest that Ceylon has been the geographical source of chromoblastomycosis. The lesion was excised and its site cauterized. There has been no sign of recurrence of the infection during the two years that have passed since the operation.