We study the conductance of single atom point contacts made between a gold STM tip and a gold layer evaporated on top of the half-metallic ferromagnetic manganite La2.3Sr1/3MnO3. The conductance histogram shows the typical peak corresponding to the last gold contact before rupture at a value smaller than the quantum of conductance, indicating that the current through the single atom contact is partially spin polarized. We discuss the possible use of this effect as a method to measure the spin polarization of spin active electronic devices. (C) 2003 Elsevier Science B.V. All rights reserved.