A survey of the River Kali in western Uttar Pradesh (India) has been carried out to assess the contribution of point and non-point sources of pollution to the river. The river shows strong seasonal dependence for various constituents and the water quality deteriorates sharply as it flows through Muzaffarnagar city. The important characteristic associated with the pollution of the river is the depletion of oxygen over a stretch of about 25 km. High values of BOD and COD indicate a high degree of organic pollution in the river. A chemical mass balance approach has been used for measuring changes in the concentration and/or load to the river, which develops an interesting concept to discriminate between point and non-point sources of pollution to the river. The resulting differential loadings, if adjusted for uncharacterized non-point contribution to the load, may represent the total point source load to the river minus any losses due to volatilization, settling, and/or degradation. Mass balance calculations conducted for certain water quality constituents indicated that additional inputs are needed to account for the observed differences in load along the river. The sources may include non-point sources of pollution due to agricultural activities, sediment remobilization or entrainment, groundwater intrusion or a combination of these sources. The difference may also be attributed to some point sources of pollution which could not be identified in the course of these investigations.