The chemical constituents of the anaerobic portion in a compost pile of cattle wastes were investigated. Cattle feces were mixed with sawdust at a mixing ratio of 4:1 to keep the moisture content at about 75% and piled up conically on the floor with weekly turning. At the first week's turning, we found out the anaerobic portion at the bottom of the compost pile cross section. Because of the insufficient supply of oxygen, an accumulation of volatile fatty acids and phenolic acids 6 times those in the starting materials was observed in the anaerobic portion which had matured less than the aerobic portion. It is important to keep compost piles in an aerobic state and prevent the formation of an anaerobic portion in order to control offensive odors and to produce good-quality compost.