A series of CCA and ACA treated hem fir plywood test boxes and untreated controls were examined after the boxes had been subjected to accelerated exposure testing for approximately ten months. The performance of untreated control stakes installed in the test boxes indicated a significant increase in the level of fungal activity in the test boxes over that known to exist in the Petawawa field test plot. Untreated hem fir plywood test panels showed evidence of advanced fungal decay, especially in the test box which had additional wood destroying fungi added to the soil. There was no sign of degradation on either the CCA or ACA treated test panels, even at the lowest retention level of 4.8 kg/m3 (0.3 pcf).