The electronic transport properties of two different systems characterized by the Dirac dispersion have been measured to high magnetic field. In the proposed topological insulator Bi2Se3, we chemically dope toward the Dirac point and find a distinct magnetofingerprint in crystals with high bulk resistivity. In experiments on cleaved few monolayer crystals of Bi2Se3, we tune the electron density with an electrostatic gate to minimize the role of the bulk and uncover metallic states in the bulk band gap. Both experiments indicate an important role for surface state conduction. Finally we study graphene- the widely studied monolayer of graphite. We find that at the Dirac point high field triggers a transition to an insulating state.