The water chemistry of 20 municipal water treatment plants in southern Sweden, representing various bedrock situations, and water qualities, were investigated. Four water samples, raw and treated. were collected from each plant and analyzed by predominantly ICP-OES and ICP-MS at four occasions from June to December, 2001. The concentrations of Ca, Mg. K.. Na, HCO3 and a number of micronutrients, varied considerably in treated waters from the studied plants (ranges; Ca: 9.1-53.7 mg L-1, Mg: 1.4-10.9 mg L-1, K: 1.1-4.8 mg L-1, Na; 5.4-75.6 mg L-1. HCO3: 27-217 mg L-1). The elimination of Fe and Mn from raw water was efficient in all treatments investigated, giving concentrations in treated waters below the detection limits at some plants. Softening filters gave waters with Ca-concentrations comparable to the softest waters in this study. Adjustment of pH by use of chemicals like lye. soda or lime, modified the consumer water composition significantly, besides raising the pH. It was estimated that drinking water contributed to approximately 2.2-13% of the daily Ca uptake, if the gastrointestinal uptake efficiency from food and water was estimated to be around 50%. The corresponding figures for Mg was 1.0-7% and for F 0-59%. None of the studied elements showed any significant time trends in raw or treated waters during the follow-up period. The concentrations of potentially toxic metals such as Al, Pb and U were low and did not indicate risks for adverse health effects (ranges; Al: 0.5-2.3 pg L-1, Pb: 0-0.3 pg L-1, U: 0.2.5 mu g L-1).