In the past, it was widely assumed that deep drainage and the resultant movement of salts, nutrients and organochlorine pesticides was negligible in Vertosols (self-mulching grey and brown clays, and black earths) of the Lower Namoi Valley, New South Wales, Australia. Recent research however has shown that in fact deep drainage does occur. The main concern, therefore, is their movement beyond the reach of crop roots. Groundwater systems in the Lower Namoi Valley have been reported to be declining, suggesting that deep drainage is not reaching groundwater. Accumulation of salts, nutrients and organochlorine pesticides (OCP’s) may, therefore, be occurring below the root zone in particular regions of the Lower Namoi Valley. The objective of this study was to estimate deep drainage using chloride mass balance models and quantify the salt, nutrient and OCP movement under selected management systems in irrigated Vertosols sown with cotton. Four experimental sites were established to study deep drainage and the movement of salts, nutrients and OCP’s in irrigated Vertosols; one at the Australian Cotton Research Institute (ACRI) Myall Vale, another near Wee Waa, a third at Merah North, which has a sodic sub-soil, and a fourth near Narrabri, which is irrigated with treated sewage effluent.