A strain, designated TN-484, producing itaconic acid with a high yield was successfully obtained by selection using an itaconic acid concentration-gradient agar plate technique after NTG-treatment of Aspergillus terrerus IFO 6365. The itaconic acid concentration produced by TN-484 was 82 g/l from 160 g/l of glucose in a shaking flask, which is 1.3-times higher than that of the parental strain, and the highest value found in a literature survey. Apart from itaconic acid, by-product organic acids were not detected in the culture filtrate by HPLC analysis. The itaconic acid yields from cells and glucose were 1.8 and 1.2 times those of parental strain, respectively. The itaconic acid concentration was also reproduced in an air-lift bioreactor with a working volume of 2.5 l.