In a 2-l stirred tank reactor (STR), maximum production rate of itaconic acid was 0.48g/l.h, for an agitation rate of 400 rpm and an aeration rate of 0.5 vvm. In an air-lift reactor (ALR) the maximum production rate was 0.64 g/l.h at an O-2 supply rate of 0.41 l O-2/l. min. Power input per unit volume which gave the maximum production rates for STR and ALR were 1180 and 542 W/m(3), respectively. If O-2-enriched air was used in place of air for ALR, the corresponding power input per unit volume was decreased to 34 W/m(3). ALR requires less power input per unit volume in comparison with that of STR whether therefore air or O-2-enriched air is used. ALR would be a suitable bioreactor for a large production of itaconic acid.