Following our observation on the intermediary metabolism of the micro-phytoplancton growing on building stone surfaces, samples taken from the Karnak temple have been examined using microbiological, histochemical and biochemical methods. To facilitate the screening procedures, the Biochemical Oxygen Demand (BOD) of 1-3 g of fine powdered samples was investigated. The oxygen consumption values found in the different samples were investigated. The oxygen consumption values found in the different examined sites range from less 0,5 more than 2 ppm (mg 02/g). Samples have been examinedmicroscopically after staining with hematoxilin Carassi and other methods. On the basis of these findings it was possible to outline the importance of biological factors in the deterioration of the sandstone of the Karnak temple.