The objectives of this study were to determine the concentrations of arsenic, copper, molybdenum, and selenium in drinking water and biological tissues (serum, urine, hair) in the populations of three rural communities in eastern Croatia, and to determine whether the concentrations of these elements in drinking water can be related to their concentrations in biological tissues. Arsenic, copper, molybdenum, and selenium concentrations were determined using inductively coupled plasma mass spectrometry in the samples of water, urine, and serum of the subjects from all three communities, while hair samples were taken from the subjects from Ćelije and Draž. The highest arsenic concentrations in drinking water and biological tissues were found in the participants from Ćelije. In all three communities, concentrations of copper, molybdenum, and selenium did not exceed maximum permissible concentrations in drinking water or in biological tissues.