We demonstrate the feasibility of applying the novel soft-X-ray magnetic circular dichroism (SXMCD) technique to investigate the magnetic properties of magnetic surfaces and ultrathin films. Measurements have been carried out on Ni films ot various thickness on a Cu(100) substrate at the Ni L2.3 absorption edges. The SXMCD data exhibit strong temperature and thickness dependence, giving film thickness dependent Curie temperatures and suggesting that a single monolayer of Ni on a Cu(100) substrate may be non-magnetic.