Isobutyl 2-cyanoacrylate monomer placed in an osseous defect excited an intense acute inflammatory response in the early stages of repair. Fibrous encapsulation of the adhesive followed, and chronic inflammation supervened for as long as the cyanoacrylate remaine. Damage to established bone, presumable due to toxic breakdown products, occurred even at a distance from the adhesive. Osteoblastic activity was retarded where cyanoacrylate was in close proximity, recovering as fibrous encapsulation and macrophage activity provided protection. Extensive marrow damage was seen, recovery similarly following fibrous protection. Repair progressed as cyanoacrylate was removed. The findings of this investigation, together with other reports of unfavourable bone reaction to isobutyl 2-cyanoacrylate (Kerr & Smyth, 1971; Corn et al., 1972) suggest that it should not be used in bone surgery. An ideal adhesive for use in bone repair should promote rather than retard osteoblastic activity, and should resorb apace with bone regeneration. Thus isobutyl 2-cyanoacrylate does not fulfil the criteria for the ideal adhesive. Hopefully, future development of the cyanoacrylates will circumvent their current disadvantages, resulting in an adhesive acceptable for clinical use in osseous repair.