Measurements of the energy distribution of field-emitted electrons with an improved retarding-potential analyzer revealed an unexpectedly narrow distribution width. Further study indicated that the tube measures the distribution in total energy of field-emitted electrons. Experimental distributions as narrow as 0.14 ev were measured. Data were obtained at liquid hydrogen, liquid nitrogen, and room temperatures and were found to be in good agreement with the new theory. The resolution of the improved analyzer is estimated to be between 0.02 and 0.03 electron volt. The experimental results obtained from the very sensitive total-energy distribution measurements serve as a further verification of the Fowler-Nordheim theory in the total-energy representation.