This article summarizes two investigations that examine the health effects of prolonged exposure to copper-contaminated drinking water. The first study was initiated after elevated copper levels were detected in several homes that were either newly constructed or recently remodeled. All of these homes were served by the same municipal water supplier. The second case involved illnesses and water-quality problems that were reported by several residents of a mobile home park shortly after a new water distribution system was installed. Findings from these investigations suggest that copper-contaminated drinking water may be a fairly common cause of nausea, diarrhea, abdominal cramps, and headaches-especially among residents of new or recently-remodeled homes, and in areas where water supplies are naturally corrosive.