The purpose of this study was to treat cutaneous melanoma metastases with topical DPCP, and then to comprehensively study the induced immune responses associated with tumor regression. Six melanoma patients were sensitized to 0.4% DPCP on one of their cutaneous metastases and their right upper arm, as well on their left lower arm. Two weeks later, effective sensitization was confirmed by noting induration at the application sites, and then challenge applications were applied to the subject’s cutaneous metastases. Also at this visit, one 0.2 mL application of 0.4% DPCP was applied to one area of non-melanoma skin, and another 0.2 mL application of 0.04% DPCP was applied to a different area of non-melanoma skin. For all patients, one of the inflamed non-melanoma sites challenged with DPCP was biopsied 3 days later. All patients continued to receive their standard oncologic follow-up and monitoring visits.