Motional narrowing of nuclear magnetic resonance lines is used to study self diffusion of aluminum in high purity aluminum and in solid solution alloys of aluminum with zinc, magnesium and copper. Diffusion parameters are determined from the experimental data using a formulation which enables the elimination of errors due to line shape changes and non-dipolar line broadenings. The results in pure aluminum yield an activation energy of 30.5 kcal/mole, with a pre-exponential factor D0 of 0.10 cm2/sec. The results in the alloys indicate that the rate of aluminum diffusion increases with increased solute content, and that the activation energy for aluminum diffusion decreases. This effect is largest for copper and smallest for zinc. Reasons for this behavior are discussed in terms of solute-vacancy binding energies.