An ideal prosthesis for ventral hernia repair should minimize development of postoperative adhesions. This study evaluates adhesion formation following intraperitoneal implantation of acellular porcine dermal collagen (PDC) and polypropylene (PP) mesh in 16 rats. Implant placement alternated left/right. Sacrifice (4 or 12 weeks) was randomized. Methods included adhesion grading (extent, severity, required dissection method) and histological evaluation. At 4 weeks, 7 of 8 PDC specimens and 0 of 8 PP implants were adhesion-free; results were identical at 12 weeks. Four-week adhesions were less developed than 12-week adhesions. Histology showed mononuclear cell foreign body reaction and disorganized collagen deposition for PPs compared to infiltration with neovascular channels and qualitatively less intense foreign body reaction for PDCs. PDC exhibits fewer adhesions and more favorable cellular response than PP in the rat.