A general n.m.r. method is described for the evaluation of chemical shifts of weak 1:1 complexes and their equilibrium quotients of formation. This method takes into consideration self-association and/or magnetic anisotropy of the acidic component. It has been applied to hydrogen-bonding interactions between phenylacetylene and a series of ethers and thioethers in carbon tetrachloride solution at 33·5°. The equilibrium quotients obtained are compared with those determined by established i.r. absorption techniques. Correlations have been observed between the equilibrium quotients and the chemical shifts, molar absorptivities, and i.r. absorption band shifts of the hydrogen-bonded species.