Discussion of the value of several chemical mildewcides in a linseed oil-base semitransparent stain for controlling mildew growth on different wood substrates at three different geographical locations. Chemicals such as pentachlorophenol and copper naphthenate were highly effective after 18 months' exposure. Effectiveness was reduced after 30 months. Results show that effective mildewcides will improve the appearance of semitransparent stain finishes used on wood for outdoor exposure. -- AATA