An investigation of the effect of discharge of domestic sewage to rivers at Kajang (Jeluh and Langat River) and coastal waters at Negeri Sembilan (Port Dickson and Blue Lagoon) was carried out. The parameters studied focused on the characteristics of sewage such as organic content (biochemiÂcal oxygen demand, BOD and nutrients (dissolved phosphate, (PO4) and nitrate (NO)). The discharge of domestic sewage from oxidation ponds near Kajang has resulted in high levels of BOD and PO4 in river water, i.e. 1.9-5.1 and 0.15-2.03 mg/L respectively. The increase in BOD is correlated (r =0.77) with the decrease in the level of dissolved oxygen (DO) in the river water. In general. the effects of domestic sewage discharge on water quality is more obvious in the Jeluh and Langat rivers at Kajang when compared to the effect on marine water.