The susceptibility of non-veneered composite panel products to decay is greater than solid timber when exposed to high moisture contents and severe decay hazard conditions. Preservative chemicals incorporated into these products at various stages of manufacture generally improve the decay resistance of these materials but certain strength properties, especially internal bond, are adversely affected. It appears from the literature survey that treatment of the composite panel products with ACA type preservative system could provide adequate protection with acceptable loss in the strength properties of the panels.