Here we have for the first time investigated the expression of peroxisome proliferator-activated receptor gamma (PPARgamma) in chronic gastritis, gastric mucosal dysplasia, and gastric carcinoma. Avidin-biotin peroxidase complex immunohistochemical methods were adopted to examine the expression of PPARgamma in 53 patients with gastric carcinoma, 18 with gastric mucosal dysplasia, 30 with chronic atrophic gastritis, and 31 with chronic non-atrophic gastritis. The positive rate of PPARgamma was 41.5% in gastric carcinoma, 27.8% in gastric mucosal dysplasia, 10.0% in chronic atrophic gastritis, and 6.5% in chronic non-atrophic gastritis, respectively. Compared with those in chronic gastritis, expression of PPARgamma in gastric mucosal dysplasia and gastric carcinoma was significantly enhanced (p < 0.05). In gastric carcinoma, expression of PPARgamma was not associated with tumor cell differentiation and metastasis to lymph nodes (p > 0.05). Taken together, overexpression of PPARgamma was apparent in human gastric cancer, which might be an early event in carcinogenesis.