The purpose of this study was to clarify the pathophysiological role of glucose and glucose transporters (GLUTs) in the proliferation and production of extracellular matrix (ECM) in peritoneal fibroblasts. Peritoneal fibroblasts from rat omentum were cultured in medium M199 with 5% fetal bovine serum (FBS) with (Group B) and without (Group A) 4% glucose. The rate of cell growth at the M stage of the cell cycle in Group B was higher than that in Group A at 12 and 24 hours after culture. However, cell numbers in Group B were less than in Group A at 24, 72, and 120 hours after culture. The GLUT inhibitor suppressed the proliferation of cells 72 and 120 hours after culture. The procollagen III peptide (PIIIP) contents in the supernatant of cells cultured in a high glucose medium were higher than those of control cells at 24, 72, and 120 hours after culture. PIIIP levels of cells cultured with the GLUT inhibitor were also higher than those of cells without the GLUT inhibitor. These results suggest that initially glucose stimulates cell proliferation and thereafter inhibits its proliferation. GLUTs may accelerate the proliferation of peritoneal fibroblasts. We suggest that glucose stimulates the ECM component PIIIP, and GLUT may have an inhibitory effect on the production of the ECM component PIIIP.