Calculations were made of the spectral density functions required for the theoretical determination of nuclear spin relaxation rates due to magnetic dipolar coupling between diffusing hydrogen spins in BCC metals. Both the like-spin (hydrogen-hydrogen) and unlike-spin (metal-hydrogen) contributions were determined using the Monte Carlo method of Faux, Ross and Sholl (1986). Results were obtained for hydrogen-to-metal ratios of 0.12, 0.3 and 0.6 for the simple hopping model (no multiple occupancy of sites) and for a multiple site-blocking model in which the hydrogen spins block all sites as far as the second or third neighbor. For the simple hopping model, the results were in very good agreement with the multiple-scattering theory of Sankey and Fedders (1980), in the high- and low-temperature limits. For the multiple site-blocking models, it was found that the BPP model (Bloembergen, Purcell and Pound, 1948) and Torrey model (1953), could differ significantly from the Monte Carlo result, particularly at higher concentrations. The results obtained for D/T1, where D was the tracer diffusion coefficient and T1 was the spin-lattice relaxation time, were compared to the experimental result on NbH0.6. The Monte Carlo method gave a value which was 2/3 of the experimental value if blocking to either the second or the third neighbor was assumed. Agreement with experiment may be obtained if it was assumed that the hydrogen diffused by a combination of jumps to nearest-neighbor and second-nearest-neighbor sites. Nuclear Spin Relaxation due to the Translational Diffusion of Hydrogen in BCC Metals. D.A.Faux, C.K.Hall: Journal of Physics - Condensed Matter, 1989, 1[49], 9919-30