Performance of a combined biofilm-electrode reactor/adsorption process for the removal of nitrate and trace pesticide from contaminated drinking water has been investigated. In long-term (more than 200 days) continuous experiments, influentand effluent concentrations of nitrate, nitrite, isoprothiolane and gas composition were measured at different electric current and pesticide loading conditions. Experimental results showed that complete and stable denitrification was achieved in BER without accumulation of nitrite and nitrous oxide. Nitrate removal ranges from O to 100% depending on electric current and inhibition by isoprothiolane was not observed. Isoprothiolane is removed by adsorption onto either granular activated carbon or silicone resin in the adsorption column. Removal efficiency of isoprothiolane exceeding 97 % was achieved and effluent concentration was below the guideline value (40μg/l). The adsorption of isoprothiolane onto GAC and silicone conformed to Langmuir isotherm model. From these results, it is concluded that the combined process is applicable to treat nitrate and pesticide contaminated drinking water. More over, from comparison with former studies, possible methods to further enhance the decomposition of pesticide were suggested.