The purpose of this study was to determine whether particulate bone graft maintains its volume when used for onlay cranioplasty. Twenty-five adult, male, New Zealand white rabbits were divided into 5 groups (n = 5/group). Groups 1 to 3 were controls: group 1, untreated; group 2, sham procedure; and group 3, burring the cortical surface. Group s 4 and 5 had augmentation of the parietal bones with particulate graft harvested from the frontal bone with a brace and bit. The particulate graft was placed on native parietal bone (group 4) or on parietal bone that had been abraded to punctuate bleeding with an electric burr (group 5). Volume maintenance and osseointegration of the grafts were determined by micro-computed tomography and histology. At 16 weeks postoperatively, the mean (SD) volumes of the parietal bones in control groups 1, 2, and 3 were 555.8 (29.2), 550.8 (36.8), and 539.0 (39.0) mm, respectively. Immediately after cranioplasty, the mean (SD) volumes of augmented parietal bone were 846.0 (10.8) mm for group 4 and 831.8 (11.8) mm for group 5. Sixteen weeks postoperatively, 100% of the group 4 grafts had resorbed (551.8 [SD, 24.0] mm), and parietal volume was no different from controls (P = 0.89). Group 5 maintained 54.2% of volume (695.6 [SD, 22.0] mm), which was greater than those of the controls (P < 0.0001). Particulate graft may be used for onlay cranioplasty if the recipient site is burred. Approximately one half of the onlay graft is resorbed, and its original shape is not maintained.