Radiata pine (<i>Pinus radiata</i> D. Don) sapwood blocks were exposed to the weather for periods of four, six, and 12 months and examined by scanning electron microscope (SEM). The combined action of sunlight, water, and oxygen produced deterioration of the cells on the surface by attacking the middle lamella and initiating delamination of cells after only four months. After six months the surface layer of cells had been completely destroyed and the underlying layer of cells had become exposed. Pit membranes and ray cells were particularly susceptible to deterioration. -- AATA