Okara (soy-residue), a cellulosic byproduct of the soymilk and tofu (soypaneer) industry, was used for the production of citric acid by solid-state fermentation using a cellulolytic Aspergillus terreus and citric-acid-producing Aspergillus niger. Okara supplemented with ammonium sulphate (0 . 10% N) when fermented by A. niger with simultaneous saccharification using A. terreus at pH 8 . 3 and incubation temperature of 30 degrees C resulted in production of 5 . 10 g citric acid/100 grams dry solids (gds) by the eleventh day.