In situ tissue dynamics were studied in 12 cases of human gastric mucosa, including normal gastric body mucosa and gastric glands with intestinal metaplasia, obtained from gastrectomy specimens of adenocarcinoma. Cell proliferation was determined by Ki67 immunoreactivity. DNA fragmentation was studied in situ by TdT-mediated dUTP-biotin nick end labelling (TUNEL). In addition, p53 expression was examined by both immunohistochemistry and mRNA in situ hybridization. In the oxyntic gastric glands, Ki67 immunoreactivity was observed exclusively in the proliferative zone and TUNEL-positive cells were present predominantly in the surface foveolar epithelium. In the gastric glands with complete intestinal metaplasia, Ki67-positive cells were present in the lower portion of the glands and TUNEL-positive cells in the superficial epithelium. In the gastric glands with incomplete intestinal metaplasia, TUNEL-positive cells were detected in the lower gastric glands adjacent to cells immunoreactive for Ki67; the proportion of these gastric glands with TUNEL-positive cells (40 out of 108 glands) was significantly higher than for oxyntic glands (94 out of 620 glands) or for glands with complete metaplasia (31 out of 254 glands). Relatively strong p53 immunoreactivity and mRNA hybridization were also observed in the proliferative and apoptotic areas of gastric glands with incomplete intestinal metaplasia. These results indicate that incomplete intestinal metaplasia is associated with increased cell turnover and p53 overexpression, possibly in response to various noxious or DNA-damaging stimuli.