We have investigated the surface magnetization anisotropy of 5 at% Co doped rutile TiO2 (1 1 0) using magnetization-induced optical second harmonic generation (MSHG) in the longitudinal Kerr configuration with an incident beam angle of 4 degrees. The MSH intensity pattern from the Co: TiO2 without surface Co clusters showed two anisotropic lobes at the second harmonic photon energy of 2(sic)omega: 3.13 eV. Since MSH intensity is proportional to surface magnetization, the result indicates an anisotropy of the surface magnetization of Co: rutile TiO2(1 1 0). This confirms the possibility that 5 at% Co: rutile TiO2(1 1 0) is a ferromagnetic dilutemagnetic semiconductor at its surface, as proposed in our previous paper. (C) 2009 Elsevier B.V. All rights reserved.