A robust sensitivity-enhanced H-1/N-14 MAS HMQC experiment is described for proton-detected N-14 NMR of solids. The sensitivity enhancement is achieved by using dipolar recoupling for coherence transfer with a so-called n = 2 rotary resonance. Rotary resonance occurs when a cw rf field matches certain ratios with the sample spinning frequency, n = omega(1)/omega(r). The theory of rotary resonance for chemical shift anisotropy, heteronuclear and homonuclear dipolar interactions is presented in the irreducible representation. It is shown that the n = 2 rotary resonance decouples the homonuclear dipolar interactions while recoupling the heteronuclear dipolar interaction for proton-detected N-14 NMR. The dipolar recoupling, T'(2) lengthening, and H-1/N-14 HMQC experiment under the n = 2 rotary resonance 2 are demonstrated. (c) 2006 Elsevier B.V. All rights reserved.