The effect of sewage sludge treatments and tree heights on chemical composition of nine years old Casuarina cunninghamiana wood was evaluated at North West Coast of Egypt.  Three treatments (control, dried sludge and sewage sludge) and three heights levels (stem base, breast height and 50% of total stem height) were investigated using different standard methods.  The results generally indicated that, wood chemical constituents were varied widely among the treatments and heights levels.  The extractives, cellulose, hemicellulose, lignin and ash contents were exhibited highly significant differences among the tested treatments. The sewage sludge treatment increased extractive and ash content, while the extractives, cellulose and lignin contents decreased with increasing of tree height levels. The determined cellulose contents at the different treatments (control, dried sludge and sewage sludge) were 41.14%, 40.28% and 44.30%, while the hemicellulose content were 29.68%, 29.11% and 26.72% respectively. From the results, there is a clear influence for sewage sludge application on the chemical composition of Casuarina wood at different height levels. This is very important to chemical technologists and wood scientists working on pulp wood quality of hardwoods.  Finally, the use of the sewage sludge as fertilizer for woody trees is a proper alternative for solving of the problems of disposal of sewage sludge. From a practical point of view, the sewage sludge application can be also increase cellulose content and reduce the lignin percentage in the treated tree. This trend can be contributed in achieve a high pulp yield from wood.