Abdominal surgery is associated with a significant risk for incisional herniation. Hernia repair is routinely performed by implantation of synthetic meshes. Such meshes may cause serious adhesions between the implanted material and organs leading to intestinal obstruction or enterocutaneous fistulas. This study compares three knitted meshes for their capacity to prevent adhesion formation in an in vivo study. The meshes evaluated are polypropylene (Prolene((R))), polypropylene coated with oxygenated regenerated cellulose-in principle-a biodegradable biomaterial (Proceed((R))), and Prolene((R)) coated with a nondegradable copolymer of the hydrophilic building block N-vinyl pyrrolidone (NVP) and the hydrophobic building block n-butylmethacrylate (BMA). The meshes were implanted in the abdomen of rats (follow-up 7 or 30 days). After 7 days, the formation of adhesions decreased in the order: Prolene((R)) > NVP/BMA-coated Prolene((R)) > Proceed((R)); after 30 days, this order changed into: Proceed((R)) > Prolene((R)) > NVP/BMA-coated Prolene((R)). Both at 7 and at 30 days, Proceed((R)) was the only mesh surrounded by macrophage cells that contained foreign materials, presumably degradation products of the (biodegradable) surface coating. The data indicate that long-term protection of implanted meshes against excessive adhesions may be achieved through stable biocompatible hydrogel surface coatings.