Soluble melanoma antigens were prepared by 3M KCl extraction. These antigens were tested by delayed cutaneous hypersensitivity reactions (DCHR) in 52 patients. Maximum reactivity was noted at 24 hours. DCHR was greater than or equal to 10 mm. of induration in 20 of 34 melanoma patients whereas only three reacted to an autologous muscle extract. Five of 18 patients with other tumors reacted to this antigen. The availability of soluble tumor antigens now permits further purification, chemical characterization, and clinical evaluation of these antigens.