['Bone perforation may induce bone marrow cell migration into a collagen sponge onlay implant. This study investigated the efficacy of bone perforation and collagen sponge onlay placement with regard to new bone formation.', 'One hundred sixty femurs of 80 Wistar male rats were used in four groups: bone perforation and sponge (PS) group: after perforating the femur, fibrillar and heat-denatured collagen (FC-HAC) sponges were placed on the femur; sponge (S) group: a FC-HAC sponge was placed directly on the femur without bone perforation; perforation (P) group: femur perforation without collagen sponge placement; and control (C) group: neither bone perforation nor sponge placement was used. Histologic and histomorphometric analyses were performed after the surgery.', 'Numerous osteoblastic and fibroblastic cells were seen during the early repopulation in and at the periphery of the sponge in the PS group. These cells were seen only at the periphery of the sponge in the S group. In the PS group, angiogenesis was noted frequently, and it exhibited significantly greater new bone area compared to the other groups at days 14 and 28.'] Do bone perforation and placement of collagen sponge facilitate bone augmentation?