Measurements of the coefficient of self-diffusion D have been carried out in oxygen-free samples of CH2Cl2, CH2Br2, and CH2I2 using spin echoes. The results show that the plots of In D vs. 1000/T are linear. The coefficients of self-diffusion decrease with increase in molecular weight and the activation energies of self-diffusion increase with increase in molecular weight. The results appear to be in agreement with the significant structure theory developed by Eyring and Ree.