Patients receive anti-cytotoxic T-lymphocyte-associated antigen-4 monoclonal antibody IV over 90 minutes immediately followed by gp100:209-217 and gp100:280-288 peptides emulsified in Montanide ISA-51 subcutaneously on days 1, 22, 43, and 64. Treatment repeats every 12 weeks in the absence of disease progression or unacceptable toxicity.