Torsion-balance tests of the weak equivalence principle

We briefly summarize motivations for testing the weak equivalence principle and then review recent torsion-balance results that compare the differential accelerations of beryllium-aluminum and beryllium-titanium test body pairs with precisions at the part in $10^{13}$ level. We discuss some implications of these results for the gravitational properties of antimatter and dark matter, and speculate about the prospects for further improvements in experimental sensitivity.