The odour generation potential (OGP) of a wastewater sample is defined to be the flux of odorous substances that can be volatilized from a unit volume of wastewater. Based on a simple first order decay of the odour concentration of a wastewater sample when subjected to volatilization, a procedure is presented to determine the OGP of different wastewater streams at a municipal wastewater treatment plant. The undigested sludge samples were identified to have significantly higher OGPs than other wastewater samples and therefore have greater propensities to emit odour. The aeration of activated sludge and the anaerobic digestion processes were found to reduce the OGPs of their respective waste streams considerably, thus confirming the effective removal of odorous volatile compounds by these two treatment processes.