Wood in use is threatened by the action of decay fungi, because these cause chemical and physical changes in wood. Thus it looses mechanical properties. If wood is used for construction purposes, we want to retain its mechanical properties as long as possible. From the security point of view, it is important that the degradation is detected as soon as possible in order to draw proper security measures. The Pilodyn 6J device can be used for early detection of decay. To determine the rate of disintegration and the depth of the Pilodyn needle penetration, we prepared oriented samples (50 mm x 50 mm x 50 mm), sterilized and exposed them to pure cultures of white-rot fungi for 3 to 21 weeks. Every 2 weeks samples were isolated and the depth of penetration of the needle in 6 directions was determined. The correlation between weight loss and the depth of penetration of the Pilodyn needle in wood was confirmed, as it was previously described for spruce exposed to brown-rot fungi.