During 13 months larvae were col- lected bimonthly at 6 sample sites and then reared to the adults. Chloride and Biochemical Oxygen Demand (BOD) were measured monthly at each sample site during 12 months in order to assess the influence of these factors on odon. distribution along the river. A total of 11 spp. were collected (I -8 spp. per site). Regression analysis indicated that odon. distribution was significantly affected by Chloride and BOD. accounting for 32.4 and 48.3%, resp. of the variation in distribution. As each variable increased, the number of spp. per site decreased.