This study was designed to elucidate the bio-degradability and self-clarification upon agricultural chemicals in the Kum river area including the field, rice paddy, green houses, the Daechung Reservoir Lake, and Kap-chun etc. First, we checked the size of bacterial populations degrading recalcitant agricultural chemicals, upon 12 different sites around Kum River area in December, 1993 and in May 1994. These recalcitrant chemicals included glyphosate(GPS), butachlor(BUT) as herbicide, cartap(CAP), diazinon(DIA) as insecticide and iprobenfos(IPR) as fungicide. Of these bacteria, the actively degradable bacteria upon agricultural chemicals were selected and isolated, for checking the growth curve and biodegradability using thin layer chromatography and U, V. spectroscopy. In winter, the densities of agricultural chemical degrading bacteria were high. As the results, the distributions and population densities of agricultural chemical degrading bacteria were very different seasonally and spatially. The order (of dominant bacterial population comprising the higher biodegradabilty upon recalcitrant agricultural chemical)was GPS→CAR→DIA→BUT→IPR, respectively. On the other hand, in spring, the order was CAR→BUT→GPS→DIA→IPR, respectively. In 6 days after each of chemicals(DIA, BUT, IPR) was