PURPOSE: Hyaluronan mediates growth of SW620 colon cancer cells. Because hyaluronan is the active ingredient in Seprafilm, we hypothesized that Seprafilm would affect intraperitoneal tumor growth in a mouse model of peritoneal seeding. METHODS: Immunodeficient mice underwent laparotomy and intraperitoneal inoculation of 10(5) SW620 cells. Seprafilm (n = 22), Vicryl mesh (foreign body control; n = 24), or no material (sham; n = 19) was placed under the incision. Mice were killed after four weeks and tumors were dissected, counted, and weighed. RESULTS: Ninety-five percent of mice in the sham group and 96 percent in the Vicryl group developed intraperitoneal tumors. In contrast, only 64 percent of mice in the Seprafilm group developed tumors (P = 0.024), and these tumors were smaller than those in the sham group; (Seprafilm = 42 +/- 9 mg vs. sham = 82 +/- 17 mg; P = 0.05). In contrast, tumors in the Vicryl group were dramatically larger (349 +/- 49 mg; P < 0.001 vs. sham or Seprafilm). CONCLUSIONS: Despite previous data that suggested that hyaluronan increases colon cancer cell growth, we found that Seprafilm decreased tumor formation and tended to decrease size in this model. In contrast, Vicryl mesh increased tumor formation and size. Our results suggest that Seprafilm does not promote intraperitoneal tumor growth, especially compared with Vicryl mesh.