It is difficult to measure chemical shifts in the small and inhomogeneous magnetic fields found in ex situ and single-sided NMR systems, such as those used for well-logging. However, it is still possible to obtain chemical information from J-coupling constants, which are independent of static field strength and temperature. We describe and analyze 1 H– 13 C double-resonance pulse sequences that are suitable for measuring heteronuclear J-coupling in grossly inhomogeneous fields. We also present preliminary experimental results from a low-frequency fringe-field system.