Pentachlorophenol (PCP) is a pesticide commonly used as a wood preservative. Although exposure has been well controlled in large chemical manufacturing plants, over-exposures have recently becomes a concern at smaller facilities. Five cases of PCP poisoning, including two fatalities, occurred in two small wood preservative plants. All cases presented with fever, including severe hyperpyrexia in two; an increased anion gap and renal insufficiency were noted in two others. PCP may uncouple oxidative phosphorylation, resulting in a poisoning syndrome characterized by hyperpyrexia, diaphoresis, tachycardia, tachypnea, abdominal pain, nausea, and even death.