The chlorinated organic pesticides BHC, DDT, Aldrin etc. which are extensively used in agriculture and public health programme are very persistent in nature. As is well known, they are lipid soluble toxic chemicals and cumulative accumulation of low concentrations of these pesticides in the body fat of mammals might pose potential hazards in the long run (Metcalf 1977). These pesticides not only exist in target organism and soil system for a considerable period of time but also enter into natural waters by percolation and runoff from agricultural land and channels, and city sewage from urban site, affecting the quality of various water sources. The persistence of these organochlorines in water has a special significance as they are taken up by unicellular aquatic organisms like plankton and thus enter into the food chain. Although some reports concerning the pollution of Ganga water by pesticides are available (Sinha 1988; Halder 1990; Agnihotri 1992) but there appears to be no systematic investigations, particularly in middle stream of Ganga and specifically in Varanasi area. Moreover, Varanasi is densely populated city and heavily pressurised by the tourists. It is also famous as one of the most important as well as popular vegetable belt in India. There are about eightyfour ghats situated at the western bank over a span of 10km and the main city ends in these ghats; the eastern bank is totally agricultural belt. Organochlorine pesticides are extensively used in both the banks for public health and agricultural purpose throughout the year. Thus it was thought worth while to monitore the levels of runoff organochlorine pesticides viz. BHC, DDT and endosulfan along with their isomers and metabolites in the Ganga water in Varanasi area.