Thin sections of rabbit papillomas reveal pools of dense virus particles in only highly keratinized cells. Viral bodies were readily distinguishable only in papillomas which had been soaked in glycerine-saline for some time. Viral bodies in fresh warts were masked by keratin, melanin and other granules. The bodies are spherical with a non-homogeneous density. They appeared to vary from 25 to 35 mμ in diameter, the most frequent size being 33 mμ. Particles in tissues soaked 1 year or 6 years were identical and equally active in test animals. Sectioned pellets of virus purified by a fluorocarbon process revealed the same particles as those seen in the tissue.