Aspergillus japonicus produces maximum extracellular tannase activity after 24 h incubation. The enzyme is produced constitutively on simple and complex sugar substrates but activity is doubled in the presence of tannic acid as sole carbon source. Parametric optimization of the enzyme yielded 1.13-fold increase in enzyme production (33.06 U/ml) at 30 degrees C and pH 6.6 with 0.2% glucose and 2% tannic acid in Czapek-Dox’s minimal medium. The enzyme shows strong end-product repression with gallic acid.