Some results of a study of the pattern of mercury (Hg) occurrence in the Katun River were used to identify the main origin of Hg in the water. A relatively simple method based on statistical analysis of concentration-discharge and load-discharge relationships was applied. The behaviour of these curves is quite different for flows polluted by sources of different origins, making it possible to separate the loads caused by point and diffuse sources. The results do not show a clear prevalence of point Hg sources, at least for hydrological periods when the water discharges are close to annual average values or higher. The results do reveal that, for the Katun River, a particular mining activity (i.e. an Hg smelter) on a tributary is not the dominant Hg source and that the contribution to the river load of surface runoff washing off Hg from the whole drainage basin may be significant.