Experimental results for the nitrogenase MoFe protein from Azotobacter vinelandii obtained by dynamic light scattering (DLS) are presented. The translational diffusion coefficient was determined to D = (4.0 +/- 0.2) x 10(-7) cm2/s. Complementary, we have performed hydrodynamic model calculations based on the X-ray crystallographic data of the MoFe protein. The calculated transport coefficient suggests that the size and shape of the protein in solution is consistent with that in the crystal structure.