Volatility of acetic acid in rice vinegar, mixed condiment of rice vinegar and acetic acid, and diluted acetic acid were investigated by head space vapor method of gas chromatography.The peak of acetic acid could not be detected by using this method, but when a considerable amount of salts was added, the peak of acetic acid could be detected and the peak height of acetic acid was in agreement with the volatility of acetic acid.With rice vinegar, the volatility of acetic acid was milder than that of mixed condiment of rice vinegar and acetic acid or diluted acetic acid.Several amino acids and several compounds which have alcoholic hydroxy group combined with acetic acid by chemical association.The volatility of acetic acid in mixed condiment of rice vinegar and acetic acid, or diluted acetic acid was depressed by the addition of these materials, resulting in the mild flavor resembling to that of rice vinegar.