We report the total volume of the limbic circuit in 12 patients and compare the volume of these structures with their reported incidence of involvement by intracranial metastatic disease. This study was performed to assess whether relative limbic circuit sparing by metastatic disease is a purely volumetric phenomenon. We contoured the hippocampus, the rest of the limbic circuit, and the rest of the brain and brainstem (from the foramen magnum cephalad, excluding the CSF spaces and pituitary) on 12 normal cranial MRI studies. We then calculated the volume of each contour, and compared these structures' volumes with their recently reported relative incidence of involvement by intracranial metastatic disease (total limbic circuit 4.9%, hippocampus 0.97%, rest of limbic circuit 3.9%). Total intracranial CNS soft tissue volumes ranged from 1117.6 -1341.3 cm3 (mean 1233.6 cm3). The total limbic circuit constituted 6.4 - 12.1% of this total volume (mean 9.2%), the hippocampus 0.63 - 1.5% (mean 1.0%), and the rest of the limbic circuit 6.0 - 11.1% (mean 8.2%). The recently reported relative proportion of intracranial metastases involving these structures among oligometastatic patients were: total limbic circuit 4.9%, hippocampus 0.97%, and the rest of the limbic circuit 3.9%. The ratios of expected/ identified involvement of these structures by intracranial metastatic disease were: total limbic circuit 1.88, hippocampus 1.0, and the rest of the limbic circuit 2.1. Sparing of the hippocampus by intracranial metastatic disease appears to be a volumetric phenomenon, as evidenced by the 1:1 ratio of (1) the recently reported relative rates of involvement and (2) the relative volume contribution of the hippocampus to the total brain volume as reported in this study. The incidence of involvement of the rest of the limbic circuit by intracranial metastatic disease is lower than would be expected by volume alone if these structures were randomly involved, suggesting that some other mechanism is involved.