Outdoor exposure studies on the performance of several finish systems on four wood-based panel products and one solid wood substrate showed that enhanced protection was found with twoand three-coat finish systems. The four panel products evaluated (hardboard siding, roughsawn redwood plywood, smooth Douglas fir plywood, and aspen waferboard) exhibited varying degrees of substrate and finish performance. Aspen waferboard had the poorest overall performance, primarily due to particle delamination and the presence of white-rot decay organisms. Best overall finish performance was found for hardboard siding, especially for opaque paint finish systems. A semi-transparent oil stain offered the least protection of all finish systems studied, due to its partial transparency to ultraviolet light. Good overall performance of all-acrylic latex finish systems on all substrates was clearly demonstrated -- AATA