An expression for the van der Waals interaction energy between two parallel torus-shaped colloidal particles is derived. It is shown that for small particle separations the torus-torus interaction energy is well approximated by the interaction energy between two parallel cylinders, each being produced by cutting a torus and unrolling it. In particular, in the limit of very small particle separations, the interaction energy between two parallel tort and that between the corresponding two parallel cylinders tend to the same limiting value. This limiting value also agrees with the result of applying Derjaguin's approximation to the interaction between two parallel cylinders. (C) 2008 Elsevier Inc. All rights reserved.