In the present comparative study of published values for the scale lengths of spiral galaxies' exponential disks, the average value of the discrepancy for more than 120 galaxies is 23 percent, with a standard deviation of 20 percent. Neither systematic trends nor correlations of discrepancies with such galaxy parameters as morphological type, arm class, or inclination, are noted. Semiautomated methods of scale-length determination are noted, however, to introduce rather large discrepancies. These results demonstrate the care with which physical intepretation of the exponential character of spiral galaxy disks should be conducted.