The Chiavenna Valley (Sondrio, Northern Italy) is located in the Central Alps and is elongated along a NNW-SSE direction. Geologically, it consists of a poly-metamorphic sequence, which includes metasediments, metagranitoids, and ophiolites, intruded by Tertiary granitoid rocks. This work describes a geochemical investigation carried out in the Chiavenna Valley (Sondrio, Northern Italy) in 2000-2002, during which more than 200 running and ground waters were collected and analysed for major, trace elements, and Sr isotopes. The great majority of the analysed waters are of good quality and have low contents of those elements considered as contaminants or undesirable substances. Thus, the Chiavenna Valley can be regarded as a mostly low-pollution area. A few metals, i.e. As, Cd, Cr, and Pb, as well as the nitrogen species, are enriched close to urban centres or/and industrial areas, suggesting an anthropogenic source. Furthermore, Sr isotopes were used to evaluate the input due to the leaching of the country rocks.