This investigation is concerned with the fineness determination of cement, comparing the air-jet sieve method with ASTM standard test methods such as hand-sieving on the No. 200 sieve, wet-sieving on the No. 325 sieve, and the specific surface by the Blaine air-permeability method. The test results indicate that: 1. The air-jet sieve method for fineness by the No. 200 sieve gives more reproducible results than the hand-sieving method, coefficients of variation for the test results of the two test methods being 2.57 and 7.93 percent, respectively. 2. The air-jet sieve method for fineness using the No. 325 sieve gives results of poorer reproducibility than those obtained by the wet-sieving method. Coefficients of variation for the test results of the two methods were 8.46 and 4.17 percent, respectively. It is suspected that the poorer reproducibility of results by air-jet sieving is due to balling of fine dry cement. There was more clogging in the wet-sieving operation even though its results were more reproducible. 3. The method of fineness determination in terms of specific surface is superior to the air-jet sieving method using the No. 200 sieve, the coefficients of variation being 0.58 and 1.98 percent, respectively. But these methods cannot be related directly because they do not measure the same parameters.