An epithelial cell line, NPC/HK1, has recently been established from a biopsy specimen of a recurrent tumour of the nasopharynx which was histologically diagnosed as a moderately to well differentiated squamous cell carcinoma. A definite decrease in the amount of tonofilaments and desmosomes in the NPC/HK1 cells during the cell line establishment was observed. The present communication reports on the fine structures of the NPC/HK1 cells heterotraneplanted in athymic nude mice.