mesh_xsections() is a Matlab function returning cross-sections of a triangulation mesh with a set of planes. Each cross-section is a cell array with one or more polygons (consecutive points in 3D). The function handles meshes with duplicated vertices (by fusing them) and open boundary edges (by cutting across the edge). It also removes duplicated faces and slightly budges mesh vertices if the plane happens to intersect them. mesh_xsections executes in a matter of seconds on meshes with hundreds of thousands of vertices.