This report describes a project to assess the accuracy of two instruments for detecting wood decay in trees in order to assess their accuracy & applicability for collecting decay data in Ontario forests. The instruments tested were the Silbert Digital MicroProbe and the Resistograph F400. In general, both instruments measure & record the resistance encountered by a thin probe as it drills through wood. The use of these instruments was compared with visually measuring decay in 60 aspen logs and 71 sugar maple logs. The instruments were also used in boreal mixedwood & tolerant hardwood stands to determine their operability under field conditions.