Ultrathin epitaxial Co films grown on a Cu(1 1 13) vicinal surface are shown to exhibit in-plane uniaxial magnetic anisotropy with the easy axis of magnetization parallel to the step edges. Along the easy axis the room temperature coercivity is in the range of a few Oe, depending on the film thickness, whereas along the hard axis no magnetic field effect in the Kerr signal could be observed up to 130 Oe.