Despite improvement of surgical treatment and application of multimodality therapies to advanced esophageal cancer, the prognosis is extremely poor for patients with unresectable tumors. Based on the genetic background of esophageal cancer, we have developed various gene therapy strategies against human esophageal cancer. In this article, we review molecular events of esophageal cancer and p53 gene therapy approaches for its treatment. First, we analyzed p53 genetic alterations and angiogenesis in esophageal cancer. Second, we tested a p53 recombinant adenoviral vector (Ad5CMV-p53). Significant growth suppression was observed following infection with Ad5CMV-p53 in human esophageal cancer cell lines. This observation suggests that Ad5CMV-p53 may be a potentially effective therapeutic agent for locally advanced esophageal cancer. Promising avenues for investigation include double gene therapy and adjuvant use of gene therapy with radiation therapy. Third, based on recent reports of clinical trials of p53 gene therapy for lung cancer and head and neck cancer, we developed a clinical protocol for p53 gene therapy for unresectable advanced esophageal cancer. This clinical trial was planned to evaluate vector tolerability and efficacy. Up to December 1, 2001, four patients were enrolled in this phase I/II trial. No serious adverse events related to Ad5CMV-p53 have occurred so far in these patients, and the trial has been safely conducted.