Continuous acetic acid fermentation was carried out using a column reactor, in which 20 to 200 thin silicone tubes ( 0.33 mm in outer diameter) were packed to supply oxygen by permeation. The highest value of volumetric oxygen transfer coefficient determined by the sulfite oxidation method was 2,860 h(-1), which was comparable to that of a well agitated and aerated fermenter. The maximum production rate of acetic acid by the bacterial films of Acetobacter aceti M7 grown on the shell-side surface of the tubes was 38.0 g/lh at an acetic acid concentration of 44.5 g/l. This was 29 times that of a continuous culture using a jar fermenter