Imiquimod (Aldara, 3M) is an immune response modifier used for the treatment of anogenital warts. We report a 55-year-old non-immunocompromised woman with extensive, human papillomavirus (HPV) 16-positive anogenital Bowen's disease. After 5 months of local treatment with imiquimod, the lesions completely regressed clinically and histologically, and HPV 16 DNA was no longer detectable. Moreover, DNA image cytometry revealed DNA aneuploidy (an indicator of prospective malignancy) in pretreatment samples but not in post-treatment samples. Therefore, imiquimod might be a treatment option for Bowen's disease, particularly in patients where other treatment modalities such as surgery are contraindicated.