In an attempt to understand some of the natural immunological characteristics of cutaneous melanoma so that we can plan justifiable immunotherapeutic approaches, 23 patients were studied. The autologous leukocyte migration inhibition assay was utilized to assess in vitro their tumor-specific cellular immunity. This assay was specifically used because when presensitized lymphocytes are exposed to the same antigen, they release lymphokines which inhibit the natural migration of the leukocytes. All the patients were staged pathologically according to the TNM system. Twelve of them had regional metastasis, i.e., stage 111, and underwent regional lymphadenectomy . The other 1 1 had distant metastases, i.e., stage IV disease, and all their gross tumors were resected. These 23 patients were the source of tumor material and peripheral blood. Fresh autologous leukocytes were obtained for the assays, from each patient, on the day of surgery and prior to the administration of the preoperative medications. These were tested in vitro, on the same day, with freshly prepared autologous tumor extracts as the source of autologous tumor antigens. The results revealed that the preoperative leukocytes of patients with stage 111 melanoma expressed hypersensitivity to their tumors, with significant inhibition of their leukocyte migration, compared to those with distant metastases who expressed no such sensitivity, P = 0.012. Such hypersensitized lymphocytes may be capable of producing more efficient lymphokine activated killer (LAK) cells for an effective adjuvant adoptive immunotherapy .