Background: The purpose of the present paper was to study the expression of cyclooxygenase-2 (COX-2) in normal squamous epithelium, squamous dysplasia and squamous cell carcinoma (SCC) of the esophagus, to elucidate the role of COX-2 in esophageal carcinogenesis, and to evaluate the in vitro effect and mechanism of a COX-2 inhibitor, NS-398, in inducing growth inhibition and apoptosis of human esophageal cancer cells. Methods: Biopsy specimens of esophageal dysplasia (n=21), and surgical resections of SCC (n=37) were compared with normal esophagus (n=37) and analyzed by RT-PCR. Human esophageal cells were used for the study. Anti-proliferative effect was measured by MTT, apoptosis was determined by DNA fragmentation assay. Results: Marked COX-2 expression was shown in SCC and esophageal squamous dysplasia, and no marked COX-2 expression was observed in the normal squamous epithelium, respectively. NS-398 could inhibit esophageal cells growth in a dose-dependent manner, induce apoptosis, and elevate caspase-3 activity in vitro. Conclusions: This study provides evidence that COX-2 is upregulated in the majority of cases of squamous dysplasia and SCC of esophagus, and that NS-398 can inhibit growth and induce apoptosis via activating caspase-3 activity in vitro. These results suggest that selective inhibitors of COX-2 may be an effective preventive and therapeutic option for esophageal carcinoma.