Persisting human papilloma virus (HPV) 2 induced common warts of a chronic lymphatic leukemia patient were orally treated with aromatic retinoid Ro 10-9359 (Tigason). Clinically, the lesions improved rapidly. Virus-specific cytopathogenic effects (CPE), virus particles and viral DNA were no longer detectable. Therapy was discontinued because of the development of a liposarcoma, which led to a complete relapse of the cutaneous lesions. HPV-2 specific parameters, CPE and viral DNA, were restored. Comparison of the restriction enzyme cleavage patterns revealed that warts before and after therapy contained the same HPV-2 subtype. The implications of the observation on the effect of Tigason on virus-induced papillomas are discussed.