In part, this chapter serves to document how far DFT has evolved in its description of noncovalent interactions, as compared to early days of unbound rare-gas dimers and convoluted discussions of which (ultimately inappropriate) semilocal XC functional should be used for weak interactions. For small noncovalent dimers, sub-kcal/mol accuracy is now achievable by means of a wide variety of different functionals, some of which include dispersion effects natively while others are explicitly dispersion-corrected. These dispersion corrections cannot and should not be equated to true dispersion energies, because the ad hoc correction is intermingled with semilocal XC effects at typical vdW contact distances, yet there are clear correlations with respect to genuine dispersion energies. Interpretative issues aside, the performance of DFT+D3, DFT+D4, DFT+XDM, and DFT+MBD is extremely promising and in small systems the accuracy of these methods is also rather similar. This is hardly surprising given the common physical underpinnings of each model, in the form of the Casimir-Polder relation between atomic polarizabilities and pairwise C 6 coefficients [Eq. ( )].