The accuracies of various nonlocal kinetic energy functionals are eval
uated by considering the kinetic energies of rare gas atoms and the ki
netic energy contributions to the interaction energy (Delta E(k)) for
pairs of rare gas atoms. The most accurate kinetic energy functionals
are those that combine the density gradient factors of accurate exchan
ge energy functionals with the Thomas-Fermi (TF) kinetic energy functi
onal; these functionals, including a new one proposed in this paper, g
ive total atomic kinetic energies to within 1%, as well as accurate va
lues of Delta E(k). Other gradient-corrected functionals give good res
ults for total kinetic energies, but give poor results for Delta E(k).