The Baikal polygon occupies the entire Lake Baikal watershed and the adjacent areas drained by the Angara and Lena rivers, including the well-known Irkutsk and Bratsk man-made water reservoirs. It is characterized by large differences of landscape, geology, mineralization and technogenic pollution. The main anthropogenic Hg-sources occur in the Irkutsk–Cheremkhovo industrial zone where chemical industries are prominent (Usolie-Sibirskoe, Sayansk, Zima). In addition, some Hg bedrock occurrences and anomalies related to faults are known in the region. In the past decade, several geochemical studies have been carried out: multi-media (stream sediment, soils, bedrock, water, snow, plants) mapping of the Baikal area (110,000 km 2, 1 site/∼100 km 2) and the Irkutsk and Osa districts (6000 km 2, 1 site/13–16 km 2); regional soil and snow geochemical monitoring profiles; geochemical studies of water reservoirs and surroundings of industrial enterprises. Hg-analyses were made using AAA (detection limit 2 ppb) and AAA with preliminary chemical concentration on sorbents (detection limit 0.02 ppb). The preliminary data indicated mean values (in ppb) as follows: bedrock 11; stream sediment 21; alluvial soil 29; Baikal bottom sediment 66; snow water 0.12; bottom sediment of the Irkutsk water reservoir 30; bottom sediment in the Bratsk water reservoir 30–6000; Bratsk plankton 130–6500; Bratsk algae 6–6500; Bratsk fish 50–6000. Three typical Hg-distribution patterns were recognized in sediment profile of the Bratsk reservoir: (1) increasing concentration from bottom to surface; (2) decreasing concentration from bottom to surface; and (3) irregular distribution of values with 1–2 maxima. The latter is typical of sites with high technogenic pollution. The strong positive correlation of Hg-contents and rates of sedimentation is also indicative of polluted sediments in the Bratsk reservoir. The Hg chemical time bomb problem can be a reality for the Baikal region. The following anomaly types were noted: (1) bedrock-related natural anomalies; (2) fault-related natural anomalies and possibly Baikal rift zone anomalies; (3) technogenic haloes near industries and settlements; (4) technogenic anomalies related to Au placer mining; (5) technogenic anomalies in dispersion flows (sedimentary bars).