A field test of untreated and preservative-treated round fence posts has been ongoing at Petawawa, Ontario since 1937. Service life data on twenty eastern Canadian wood species was developed. In addition, treatments by a variety of pressure and non-pressure processes with waterborne and oilborne preservatives were tested. Thermal immersion in creosote was the most effective non-pressure method used. Brush treatments and cold soaking proved to be ineffective for long-term protection from decay. Pressure treatment utilizing standard waterborne (CCA and ACA) and oilborne (creosote, pentachlorophenol, and copper naphthenate) provided excellent protection from decay.