OBJECTIVES: I. Determine the effect of PSA-3 peptide vaccine emulsified in Montanide ISA-51 on PSA levels in patients with recurrent prostate cancer. II. Determine the toxicity of this regimen in these patients. III. Determine whether the T lymphocyte immune response to PSA-3 and HLA-A2 antigen-presenting cells that endogenously produce PSA is increased in patients treated with this regimen. IV. Determine the duration of the PSA and/or immune responses in patients treated with this regimen. V. Correlate immune and PSA responses in patients treated with this regimen. VI. Determine the efficacy of a second (boost) vaccination with this regimen in patients with a PSA or immune response.