Spin-polarized electron tunneling between a Ni tip and a self-assembled monolayer, consisting of sigma-bonded bicyclo[2.2.2]octane-1,4-dithiol molecules, deposited on Ni(111) surface is calculated by density functional approach within Bardeen, Tersoff, and Hamann formalism. The magnitude of the tunneling current is predicted to depend on the spin alignments of the probe tip and the substrate. Comparison with a similar study involving benzene-dithiol, a pi-conjugated molecule, suggests that the magnitude of the tunnel current as well as the spin-dependent current is strongly influenced by the nature of the chemical bonds in the molecular structure. (c) 2006 Elsevier B.V. All rights reserved.