The performance of a bone biopsy results in a dramatically altered magnetic resonance image (MRI) signal in both the biopsied segment and the surrounding bone. An experimental canine model was used to determine the cause and imaging sensitivity of this postbiopsy signal change in the adjacent intraosseous contents. Six dogs were used in the study. Half of the dogs had the cortical window left open, and the other half had a polymethylmethacrylate plug inserted. After hemostatic closure, images were obtained immediately postbiopsy and 6 weeks thereafter. MRI defect length was examined on both T1 and T2 weighted sequences at both time periods. After the final image was taken at 6 weeks, the bone was harvested and examined grossly and histologically for the purpose of making pathoradiographic correlations. The results suggest that magnetic resonance imaging is a sensitive method that accurately reflects the defect caused by bone biopsy and the surrounding hemorrhage. The defect length increased in size over time. The image was slightly smaller than the corresponding histologic response. Insertion of a cortical plug had no predictable effect on defect length, which depended upon the amount of pressurization used during insertion. We conclude that MRI may be useful in the staging of intraosseous primary neoplasms of bone after bone biopsy, especially in the detection of an iatrogenically induced tumor/hemorrhage margin. This may be critical when planning an intraosseous surgical resection in which short, wide margins are anticipated.