&NA;The aim of the study was to evaluate the mechanical performance and the structure of neoformed bone around hydroxyapatite‐coated titanium fixtures according to guided bone regeneration techniques. Ten hydroxyapatitecoated titanium fixtures were inserted in the femurs of five rabbits, in which a cortical defect was created and after the insertion of the fixture, covered with a resorbable membrane obtained from bovine Achilles tendon collagen Type I (A implant). In the same femur, a second fixture was inserted in similar cavities without application of the membrane (B implant). After 60 days, the animals were sacrificed, and block sections of the femoral bone con taining the implants were embedded in polymethylmetacrylate and subjected to tensile shear‐stress at break testing. After the detachment of the implants from the bone, their surfaces were examined with a scanning electron microscope. Tensile shear‐stress values for A and B implant specimens were comparable to some extent, but the former had a lower performance. In this regard, scanning electron microscope observations showed that the neoformed cortical bone present cervically around implant A was much thicker than around implant B. (Implant Dent 2000;9:219‐225)