The reactivity of Pt3Sn(111) has been tested in the 1,3-butadiene hydrogenation reaction and compared to that of Pt(111) by a combination of polarization modulation absorption reflection infrared spectroscopy, mass spectroscopy and gas phase chromatography techniques. Pt3Sn(111) is less active than Pt(111) by one order of magnitude but it is more selective into butenes whatever the initial surface structure p(2 x 2) or (root3 x root3). (C) 2004 Elsevier Inc. All rights reserved.