Several families of Talca city, Chile complained to health authorities for what they attributed to consumption of copper (Cu)-contaminated drinking water. We assessed the situation 6-12 mo after the initiation of complaints by characterizing the symptoms reported, the chemistry of drinking water, and the Cu concentration in stagnant drinking water. After completing a census, 1778 households accepted participation and were categorized as follows: category 1, Cu plumbing for tap water and dwellers reporting health complaints (HC); category 2, Cu plumbing for tap water and dwellers reporting no HC; category 3, plastic plumbing for tap water and dwellers reporting no HC. Questionnaires recorded characteristics of households and symptoms presented by each member of the family in the last 3 mo. The Cu concentration in drinking water was measured in a subsample of 80 homes with Cu pipes. In category 1, participants presented significantly more abdominal pain, diarrhea, and/or vomiting (gastrointestinal [GI] symptoms) in comparison to category 3 and to categories 2 plus 3. The stagnant Cu concentrations measured in drinking water in all houses studied were below the US Environmental Protection Agency guideline value (<1.3 mg Cu/L). In summary, data obtained by interviews suggested that individuals in some areas of Talca city were suffering more GI symptoms potentially related to Cu excess, but measurement of Cu concentration in stagnant tap waters ruled out the association between Cu exposure and GI symptom reports at the time of this study. The dose-response curves for GI symptoms and Cu exposure now available were crucial in the analyses of results.