We report here the first measurements of the complete valence shell binding energy spectra and the highest occupied molecular orbital (HOMO) momentum profile of butanone using the binary (e,2e) electron momentum spectrometer, at an impact energy of 1200 eV plus the binding energy and using symmetric non-coplanar kinematics. The experimental momentum profile of the highest occupied molecular orbital is compared with the theoretical momentum distributions calculated using Hartree-Fock and density functional theory methods with various basis sets. The experimental measurements are well described by density functional theory calculation. (c) 2005 Elsevier B.V. All rights reserved.