SummaryInformation on the natural decay resistance and efficacy of CCA-treated rubberwood is important for the development rubberwood industry. The purpose of this study was to determine the natural decay resistance of rubberwood and the efficacy of CCA-pressure treatment in order to explore a new opportunity for this abundant raw material. Natural decay resistance and efficacy of CCA was estimated using soil-block test according to AWPA E10-91. Cubes were exposed to six wood-decay fungi: two each from white, brown, and soft rot. The moisture content of test cubes exposed to Irpex lacteus and Trametes versicolor increased with weight loss increase, while that exposed to Gloeophyllum trabeum and Postia placenta decreased. After a 12-week incubation period the average weight loss by white rot and brown rot fungi was about 1.5 times higher than that of soft rot fungi. CCA retention of 4.1 kg/m3 reduced weight loss to between 8% and 10%, retention of 14.5 kg/m3 protected weight loss by all test fungi from exceeding 2%.