49 active ingredients of agricultural and industrial fungicides, insecticides and herbicides were assessed as wood preservatives against fungal and insect attack. Timbers used were <i>Pinus radiata and <i>Betula alba. The materials being tested were alkyl ammonium derivatives, possible alternatives for the commonly used copper-chrome-arsenate and pentachlorophenol wood preservatives. Nopocide and Melprex were found to be effective as both insecticides and fungicides and Skane M-8 and Buson 30 as fungicides but not as insecticides. Podan showed high insect toxicity but low fungicidal activity. Five other chemicals were effective fungicides at 1.0% concentration. The remainder were ineffective.