The reaction conditions were optimized for enzymatic hydrolysis of pectic substances using pectolytic enzymes produced by Aspergillus niger NCIM 548. Response surface methodology was used to optimize the reaction parameters and the central composite design was employed for this purpose. Pectin was used as the substrate for polymethylgalacturonase and pectinlyase, whereas polygalacturonic acid was the substrate for polygalacturonase. The volume ratio of reactants for maximum hydrolysis was determined under the assay conditions. The optimum amount of substrate and enzyme were found to be 0.2 cm(3) and 0.074 cm(3) for polymethylgalacturonase, 0.4 cm(3) and 0.086 cm(3) for polygalacturonase, and 0.63 cm(3) and 0.7 cm(3) for pectinlyase. The pH and temperature optima were found to be 5.3 and 30 degrees C for polymethylgalacturonase, 6.6 and 26 degrees C for polygalacturonase, and 4.8 and 35 degrees C for pectinlyase. Under optimized conditions the enzyme activities were higher when compared to unoptimized conditions.