This paper reviews copper naphthenate (CuNap) and its utility as a treatment for wooden utility poles. One of the principal reasons that CuNap has gained market acceptance, in addition to its efficacy against decay fungi and wood-destroying insects, is its low mammalian toxicity. CuNap is a well-proven non-restricted use preservative, used extensively and specified for environmental reasons by utilities across the US, and recently adopted by a Class One railroad to replace creosote in both their poles and ties. This paper reviews the efficacy of CuNap in laboratory and long-term field tests with an emphasis on the properties of wood treated with CuNap, including permanence of preservative, conductivity and climbability. An update on the regulatory status of copper naphthenate is also given, including disposal options for treated wood. CuNap is already likely to increase in importance due to both economic and efficacy performance, but future disposal concerns are also likely to increase its specification as a preferred preservative system.

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