Stakes of various wood species as well as composite material of different species (plywood) were pressure-treated using a variety of preservatives and chemical loadings. Each stake is buried to half its length at the Petawawa Forest Experiment Station -- near Chalk River, Ontario. The oldest stakes in the plot are treated with copper abietate/pole oil and after 21 years all of the stakes are still performing well. Red pine stakes treated with copper chrome arsenate type B are also performing well after 19 years of service. Performance of the stakes is monitored yearly by examining each stake and assigning a rating according to the severity of decay present. Performances of the treated stakes are compared to untreated controls of the same species installed in the same plot. Preservative effectiveness is expressed as the average number of years in service over the percent stakes remaining in service at the time of examination. One hundred and twenty seven series of stakes are currently under test. Stakes treated with zinc thiocyanate and zinc thiocyanate/latex are performing better than expected to date.