Combined low-temperature NMR/UV-vis spectroscopy (UVNMR), where optical and NMR spectra are measured in the NMR spectrometer under the same conditions, has been set up and apVied to the study of H-bonded anions A center dot center dot H center dot center dot X(-) (AH = 1-(13)C-2-chloro-4-nitrophenol, X(-) = 15 carboxylic acid anions, 5 phenolates, Cl, Br(-), I, and BF(4)(-)). In this series, 5 is shifted from A to X, modeling the proton-transfer pathway. The (1)H and (13)C chemical shifts and the HID isotope effects on the latter provide information about averaged H-bond geometries. At the same time, red shifts of the pi-pi* UV-vis absorption bands are observed which correlate with the averaged H-bond geometries. However, on the UV-vis time scale, different tautomeric states and solvent configurations are in slow exchange. The combined data sets indicate that the proton transfer starts with a H-bond compression and a displacement of the proton toward the H-bond center, involving single-well configurations A-H center dot center dot center dot X(-). In the strong H-bond regime, coexisting tautomers A center dot center dot H center dot center dot center dot X(-) and A(-)center dot center dot center dot H center dot center dot X are observed by UV. Their geometries and statistical weights change continuously when the basicity of X(-) is increased. Finally, again a series of single-well structures of the type A(-)center dot center dot center dot H-X is observed. Interestingly, the UV-vis absorption bands are broadened inhomogeneously because of a distribution of H-bond geometries arising from different solvent configurations.