Activated sludge models are a reliable and useful instrument in design and management of wastewater treatment plants. The biochemical nature of the processes involved the models which need a specific calibration to local conditions. A common method to determine kinetic and stoichiometric parameters of the biomass or wastewater is respirometry. The aim of this work is to determine the heterotrophic growth rate (μH) and decay coefficient in Egypt using respirometric test method which was not determined before in Egypt. It was found that the value of μH and bH for the wastewater obtained from Al Qenayat wastewater treatment plant was 4.79 d-1 and 0.6 d-1 respectively.