The potential benefits of platelet-rich plasma in the healing of isolated defects are unclear. The purpose of this study was to evaluate the effects of PRP on bone healing in titanium bone chambers, which represented isolated defects. PRP was prepared from blood collected from six adult female albino New Zealand rabbits. Titanium bone chambers with a 4-mm inner diameter were implanted into the tibiae of each animal at baseline and 2 weeks later; chambers healed for 6 or 8 weeks, either with PRP (test) or without PRP (control). Bone chambers were harvested from each animal and processed for histologic evaluation. Bone formation in 8-week test samples was not significantly different from that of the 6-week test samples. In control samples, more bone formation was seen at 8 weeks than at 6 weeks. The fibrous tissue content in control samples was higher than that of the test group in superficial sections, revealing that the tissue differentiation rate was higher in the test chambers. Time-dependent bone tissue differentiation in bone chambers augmented with PRP is higher than in normal wound healing, and PRP seems to increase the rate of tissue differentiation in early healing.