Histopathologic studies and fluorocytometric DNA analysis were carried out in 39 patients with intestinal metaplasia (IM) of the mucosa associated with gastric carcinoma, in order to determine possible relationships. According to the histological degree of IM, 39 cases were divided into 16 (41%) with slight-to-moderate, and 23 (59%) with severe IM. The 39 tumors were histologically divided into 20 (51%) differentiated tumors and 19 (49%) undifferentiated tumors. The DNA patterns of tumors revealed 17 (43%) to be euploidy and 22 (57%) to be aneuploidy. The DNA content of the metaplastic epithelial cells was measured, and the percentage of the cells in S and G2 + M phases of the cell cycle was taken as the index of proliferative activity. DNA analysis of the non-metaplastic epithelium was performed in 10 as a control group. While the histological differentiation of the tumors and the degree of IM were not related to the proliferative activity of IM, the IM around the aneuploid tumors did have higher proliferative activity (14.01 +/- 6.16%) than that around euploid tumors (11.08 +/- 7.13%) or of normal mucosa (9.95 +/- 9.92%). This approach will help to determine cell kinetics of IM around the gastric tumor. Our study indicated a relationship between DNA ploidy and the proliferative activity of IM around gastric cancer.