This report covers the results from the second year of a two-year carcinogenicity bioassay of the tissue adhesive, isobutyl 2-cyanoacrylate (IBC). The IBC was administered by surgical implantation of the liquid monomer directly onto the ventral capsule of the liver. A dose-related increase in the incidence of clinically observed intra-abdominal masses was evident among IBC-treated animals of both sexes. In addition to the masses and the more permanent sequelae of the surgical procedure (xyphoid protuberance, corneal opacity), the animals presented with a variety of transitory clinical signs sporadically though the first and second year. These signs were observed in all dose groups, and could not be attributed to compound administration. Results of this study indicate that the presence of IBC in the abdominal cavity had no effect on survival, weight gain, or the clinical condition of F-344 rats during the second year following its implantation. IBC did produce sarcomas in the abdomen of 16% of the animals. The sarcomas were attributed to a solid-state effect which is not present in man. A nonstatistically significant increase in hepatocellular carcinomas was observed in 4 IBC-treated rats but there was no clear evidence that this could be attributed to the IBC implants. Keywords: Chronic toxicity; Mammalian toxicology; Tissue adhesive; Carcinogenicity bioassay; Rats.