A pilot scale slurry bioreactor was used for the treatment of food wastes. Food wastes were continuously added (750 g wet weight per day) into the reactor and successfully decomposed to inorganic carbon without intermittent removal of suspended solids. During operation for 90 days, 91% reduction of food wastes was achieved. Microorganisms actively grew during the initial 20 days of operation, and reached a stationary phase with a cell concentration of around 5 x 10(10) cells ml(-1), which indicated that food waste was utilized as a respiratory substrate during this phase. Using data for time variation of dissolved oxygen, the oxygen requirement for decomposition of food wastes was estimated to be 5.0g O-2 g(-1) dry weight of food wastes.