This experiment was conducted to investigate the distributions of free sugars in commercial liquid yogurts as well as the changes of their sugar contents during the storage at different temperatures by HPLC. The results obtained were as follows: 1. The optimal operating conditions of HPLC for the detection of free, sugars in sample were as follows: mobile phase, acetonitrile + water = 78+22 (v/v); flow rate, 2㎖/min.; the chart speed of recorder, 0.25 ㎝/minute. Under the above conditions, fructose, glucose, sucrose and lactose were not only seperated at base line within 16 minutes but also quantitated by peak height. 2. The extraction of sugars is sample by ethanol was much better than that of acetonitrile. 3. Fructose, glucose, sucrose and lactose were isolated from all products examined (A.B.C.D); among these, sucrose was largest in quantity, and the others wore is order of glucose, fructose and lactose respectively. 4. The changes in sugar content after 7 days` storage at different temperatures showed that glucose, fructose and sucrose were all decreased while lactose was almost unchanged.