Orange finisher pulp, a juice processing by-product, was investigated as a substrate for polygalacturonase (PG) production by Rhizopus oryzae (ATCC 24563) via solid state fermentation. PG activity was indicated by increase in liquefaction and uronic acid solubilization and subsequent decrease in pectin content of the solid fraction over a 5-day fermentation. Partial characterization of the enzyme extract indicated pH optimum 5.0 for PG. Viscosity and reducing sugar measurements suggested endohydrolytic activity. Little or no pectinesterase, pectin or pectate lyase activities were detected; therefore, potential for direct utilization of the PG exists in the citrus industry. Orange finisher pulp was a suitable substrate for fungal PG production.