The usefulness for cancer therapy of replication-competent adenoviral vectors expressing therapeutic genes from the E3 region has been evaluated, but few reports have described replication-competent adenoviruses with insertions at the E1 region in the full viral genome. We investigated in different prostate cancer cells the oncolytic efficacy of the replication-competent adenovirus 11p vectors expressing adenovirus death (RCAd11pADP) and red fluorescence (RCAd11pRFP) proteins from the upstream E1 region. ADP/RFP gene expression was 2-3 logs higher in PC3 and DU145 cells than in LNCaP and RWPE-1 cells. E1A protein expression in PC3 and DU145 cells was notably increased after infection with the RCAd11pADP or RCAd11pRFP vector compared with the Ad11pwt virus. Toxicity assays revealed 2-5-fold greater oncolytic effects of RCAd11pADP compared to Ad11pwt. Although all three viruses suppressed subcutaneous PC3 tumour growth in nude mice, RCAd11pRFP had greater oncolytic effects than did the Ad11pwt virus, and RCAd11pADP exhibited significant anti-tumour effects via apoptosis in a xenograft model. Interestingly, the apoptosis triggered by RCAd11pADP was markedly enhanced in comparison to that by the vector expressing ADP from E3 region. Taken together, our findings suggest that RCAd11pADP can potentially be used for the treatment of prostate metastases in clinical settings.