1. The clinical condition is described with special reference to etiology. 2. The similarity in the histology of all papillomata is noted. The connection between genital warts, common warts and laryngeal papillomata is considered. 3. These papillomata are examples of a transmissible tumour in man. 4. These tumours are similar to the Shope papilloma of rabbits. 5. The older and more recent theories of the etiology are discussed. It is concluded that these warts are probably caused by a virus the nature of which must remain in doubt at present. 6. Attempts were made to transmit the lesion to animals. It was found that mice, guinea pigs, rabbits and a monkey were all unsuitable, probably owing to the species specificity of the virus.