The relationship between the low-frequency (annually averaged) salinity and oxygen concentrations in the last 30 years in the Baltic Sea and the large-scale atmospheric circulation has been statistically analyzed. It has been found that at these time scales the evolution of salinity and oxygen is quite homogeneous in depth, i.e. deviations from the long-term mean tend to be of the same sign in the upper and deeper layers simultaneously. Moreover, the evolution of the salinity and oxygen concentrations are negatively correlated within each layer: lower than normal salinities tend to be observed simultaneously with higher than normal oxygen concentrations, and vice versa. The statistical analysis seems to indicate that the forcing by the atmospheric circulation may be responsible for this anticorrelation between salinity and oxygen. Stronger meridional sea-level-pressure gradient over the North Atlantic, and therefore stronger westerly winds, cause positive rainfall anomalies in the Baltic Sea catchment area and increase run-off giving rise to decreased salinities at all depths. The mechanisms by whi ch a stronger zonal atmospheric circulation enhances the oxygen concentrations m ay be related either to a weakened stratification through the reduced salinity ( at long time scales), or by stronger or more frequent inflows of North Sea water s (at short time scales). The influence of the atmospheric circulation may explain at these time scales of the order of 60% and 40% of the variability of these hydrographic variables, respectively. The question has also been addressed of how salinity and oxygen in the Baltic Sea may respond to changes of the atmospheric circulation in a global climate change scenario. For these purpose the intensities of the relevant atmospheric circulation patterns in a transient experiment with a coupled atmosphere-ocean General Circulation Model forced with increasing anthropogenic greenhouse gases concentrations between the years 1860 and 2099 have been estimated. In this integration the change of the atmospheric circulation most relevant for salinity and oxygen in the Baltic Sea seems to be an enhancement of the meridional sea-level-pressure (SLP) gradient in the North Atlantic. Thus, under the assumption that the statistical relationship between SLP and the hydrographic variables also holds in the future, this trend in the atmospheric circulation would lead to decreased salinity and improved oxygen conditions in the Baltic Sea.