The appearance of residues of nine herbicides, namely atrazine, diuron, hexazinone, 2.4-D.linuron, ioxynil, paraquat, oxyfluorfen and picloram which are often used in weed control in sugarcane and of one insecticide (carbofuran) were monitored at fortnightly intervals during 1995 and 1996 in groundwater from 20 boreholes representing the 10 main groundwater basins of Mauritius and in surface water at 25 locations along the rivers forming part of the Grand River North West catchment area. The data showed that only the residues of the following three herbicides: atrazine, hexazinone and diuron could be detected in freshwater sources in Mauritius. More than 60% of the groundwater analysed (> 50% for river water) in fact did not contain any herbicide residue. Even when present, the levels of the herbicide residue were mostly within the range of 0.05 to 0.5 ppb. More importantly, their highest concentration recorded rarely exceeded the recommended maximum limits of 3 ppb atrazme, 14 ppb diuron and 210 ppb hexazinonc. The frequency or appearance of the herbicide residues is not related to the piezomelric depth of the groundwater and to the lime of herbicide application. High intensity rainfall events had a greater impact than period of application on the appearance of herbicide residue in the ground and surface waters. Nevertheless though the period of herbicide application alone had little bearing on the pollution or freshwater sources by herbicides in Mauritius, the level of the residue in rivers fed by runoff water frorn adjoining fields rose as the time interval between date of herbicide application and the arrival of the high intensity rainfall shortened. The present study therefore showed that although no freshwater source in Mauritius is sheltered from possible contamination by herbicides used in sugarcane, the public fear and mistrust of herbicides used in Mauritius are not justified as the level of herbicide residue in water would not pose a risk to human health.