For high-resoln. 13C NMR spectroscopy under conditions of complete proton decoupling, gated decoupler and proton flip methods are described which demonstrate that heteronuclear J spectroscopy can provide fine structure information even in very inhomogeneous magnetic fields. The spectrum is broken down into sep. responses from individual C sites in the mol. and the magnetic field inhomogeneity is no longer a fundamental limitation on the resolving power since spin-echo refocusing methods are used to counteract the dispersal of signal components from different regions of the sample. The expt. extends the principle of J spectroscopy to the case of heteronuclear spin-spin coupling. The technique is illustrated by the proton-coupled natural abundance 13C spectrum of pyridine. [on SciFinder (R)]