Dipole moments have been measured for a number of hole-transporting donor compounds. Where possible, the results are interpreted in terms of group dipole moments and molecular conformations. The mobility of holes in molecularly doped polymers containing some of these compounds generally (but not universally) correlates with the dipole moment of the donor, consistent with previous results. Compensating effects that apparently contribute to the correlation are pointed out, as are difficulties in constructing an "equitable" comparison of disparate materials. The physical origin of the correlation is discussed. An appendix presents formulas for the distribution of possible hole energies for a donor molecule containing a dipolar substituent with a rotational degree of freedom.