Pentachlorophenol is used as an industrial wood preservative for utility poles, crossarms, fence posts, and other purposes (79%); for NaPCP (12%); and miscellaneous including mill uses, consumer wood preserving formulations and herbicide intermediate (9%). Photolysis and microbial degradation are the important chemical removal mechanisms for pentachlorophenol (PCP) in water. Direct photolysis may be an important environmental sink for PCP present in the atmosphere. Soil degradation studies indicate the PCP is biodegradable; microbial decomposition is an important and potentially dominant removal mechanism in soil. Monitoring studies have confirmed the widespread occurrence of PCP in surface waters, groundwater, drinking water and industrial effluents. Subchronic and chronic toxicity studies show adverse effects in the liver, kidney and immune system. Inadequate evidence exists for carcinogenicity.