Diphencyprone is a potent contact sensitizer sometimes used to treat alopecia areata and cutaneous warts. A patient with previous primary nodular melanoma on the scalp developed extensive, confluent cutaneous metastases near the primary site, unsuitable for treatment with surgery or radiotherapy. Topical treatment with diphencyprone as a single agent resulted in regression of all lesions, and the patient remains well 18 months later. Topical immunotherapy with diphencyprone was an inexpensive and well-tolerated treatment for extensive cutaneous melanoma metastases in our patient unsuitable for other therapies.