None of the pulmonologists or the biophysicists in my quick, unscientific poll of experts in diffusing capacity are using Dmco or Vc for clinical reasons, at least in part because of the technical difficulty of obtaining high-quality results. Accurate measurements require Dlco to be measured using several different oxygen concentrations, and using too few concentrations can adversely influence the test results. Plummer1 reports that 7,941 Medicare claims for code 94725 were submitted in the year 2000. In 2006, the number of claims for this code rose to 87,496. Since the clinical utility has not been expanded in this time and the use of the measurements has not gained acceptance in leading laboratories, this increase may indicate a misunderstanding of the tests at best and mere revenue enhancement at worst. Payment issues for clinical measurements of Dmco or Vc should be reconsidered. If the codes are recommended, it would be wise to include them as tests published as “limited coverage” and include specific clinical criteria for their use.