Abstract: Biopsy specimens taken from 80 patients with condyloma accuminatum were studied The koilocytes were observed under light micro-scope in all patients. Among 30 cases assayed for HPV-Ag with PAP staining, twelve were positive (40%). Viral particles were detected in the upper most layers of epithelium in 5 out of 15 cases. The koilocytes were large vacuolated cells characterized by enlarged nuclei with wrinkled nuclear membranae and clumping chromatin. They had the appearance of loose cytoplasm with scarce organellae acid the tonofilament bundles chiefly located in the peripheral cytoplasm. Our observation suggests that the vacuolation of swollen mitochondria and dissolution of glycogen particles as well as the dilatation of small vesicles of some epithelial cells resulted in the formation of the so-called "koilocytes". These appearances were probably the cytopathic effect of HPV infection.