We have constructed a prostate-specific lentiviral vector based on the promoter of the prostate-specific antigen (PSA). The PSA promoter-based lentiviral vector has been used to deliver the diphtheria toxin A (DTA) gene into prostate cancer cells, and has shown promising tissue-specific eradication of prostate cancer cells in cell culture. To evaluate the efficacy of eradicating human prostate cancer cells in vivo, we used human LNCaP prostate xenografts in nude mice as an animal model and found that with a single injection of the DTA lentiviral vector into LNCaP prostate tumors, approximately 75% of the tumors (from three experiments; conducted 9/11, 11/15 and 3/4) in the animals were completely eradicated. The DTA vector has also shown the ability to cause tumor regression in recurrent prostate tumors. Intravenous injection of the DTA lentiviral vector into nude mice elicited no pathogenic effects, suggesting that this prostate tissue-specific vector is safe for eradicating prostate cancer cells in vivo.