This paper presents a novel hybrid segmentation technique incorporating a statistical as well as a geometric model in a unified segmentation scheme for brain tissue segmentation of magnetic resonance imaging (MRI) scans. We combine both voxel probability and image gradient and curvature information for segmenting gray matter (GM) and white matter (WM) tissues. Both qualitative and quantitative results on synthetic and real brain MRI scans indicate superior and consistent performance when compared with standard techniques such as SPM and FAST.