 The purpose of this research study is to test a new treatment for prostate cancer. We have been exploring the use of cytokine immune stimulating gene therapy by directly injecting a virus which produces a cytokine called interleukin-12 IL-12 into the prostate gland to control tumor growth. We propose to explore the use of adenovirus-mediated human interleukin-12 Ad.hIL-12 in patients with recurrent non-metastatic prostate cancer following radiation therapy in a Phase I trial. Participants will be placed in rising dose groups with the primary endpoint of learning the maximum dose that can safely be given by injection directly into the prostate gland. Toxicity will be determined through physical examination, laboratory values, and blood levels of cytokines. Evidence of an immune response against prostate proteins will also be monitored. If the treatment works, the cancer will shrink or not grow. This will be monitored by prostate specific antigen PSA levels in the blood. However, we do not know if this treatment will be effective. If the PSA continues to rise after treatment, participants will be taken off study and offered other treatment. There is no compensation for participation in this research study. There will be no charge for the treatment with gene therapy or the monitoring associated with this research study. Monitoring will occur in a specially designated clinical research center. 