The first evidence of interest in the chemical oceanography of the Baltic Sea appears to be the early studies of the chemical composition of sea water. The proportions of the conservative elements in sea water are usually expressed relative to chlorinity and the anomalies are defined relative to the proportions of these elements in ocean water. Because of the unusual hydrographical features of the Baltic Sea, it might be expected that these elements would show significant anomalies. More than 200 rivers annually discharge about 450 km3 of fresh water from drainage areas in different geological environments. In addition, the water added to the Baltic Sea by precipitation has a chemical composition that differs significantly from that of distilled water. The situation is further complicated by the presence of dissolved organic substances having considerable complexing properties, for example, humic substances, and by variations in the redox conditions. When these factors are considered, it is surprising that the relative proportions of the major elements in Baltic Sea water are so similar to those in the ocean water.