Abstract Deuterium spin relaxation has been studied as a function of temperature, concentration, and site of deuteration for both components of a binary nematic liquid-crystal mixture of 4-methyl-4′-cyanobiphenyl- d 11 (1CB) and 4- n -pentyl-4′-cyanobiphenyl- d 6 (5CB). Relaxation rates of Zeeman order R 1Z and quadrupolar order R 1Q were determined by two different techniques. It was found that the standard method, based on sum and difference (SAD) magnetization generated by a Jeener-Broekaert sequence, suffers from serious systematic error due to frequency-selective excitation, large linear phase corrections, and unavoidable baseline distortion. Broadband Jeener-Broekaert (BBJB) sequences can be used to achieve uniform excitation of quadrupole order, while echo techniques can be used both with inversion-recovery (IR) and BBJB sequences to eliminate baseline artifacts. This new approach of performing two separate experiments (IR/BBJB) yields spectral densities J 1 ( ω 0 ) and J 2 (2 ω 0 ) with precision and accuracy significantly greater than those determined by the SAD method. For 1CB, the SAD results were not accurate enough for detailed analysis but a satisfactory interpretation of the temperature-dependent IR/BBJB data for 1 CB methyl and aromatic deuterons was achieved in terms of a model with three correlation times. The same model was successfully used to account for relaxation of the alkyl chain C, deuterons in the liquid-crystal molecule 5CB. Measurements on 10 and 25 mol% mixtures showed that the correlation times and activation energies for rotational motion of both 1CB and 5CB are concentration independent.