Clinical trials have fully confirmed the eflicacy of podophyllin for topical use in the treatment of condylomata acuminata. The application of podophyllin to normal human or rabbit skin caused changes in the epidermis. There was alteration of the nuclear pattern with disintegration of chromatin. There were cytoplasmic changes involving spongy swelling, shrinkage from the cell membrane, hydrops, delicate fibrillation, and alterations of standing reactions. In rabbits, an essentially normal epidermis was reestablished 4-6 days after a single application and a resistance was established. These abnormal cells resembled "colchicine figures", and when colchicine suspensions in oil were applied to condylomata acuminata, the pathologic alterations were similar but more intense and briefer. Neither podophyllin nor colchicine had any effect when applied to lesions with extensive keratiniza-tion, indicating that their penetrating power is slight.