The objective of this study was to determine whether sensitive populations are adversely affected by sudden exposure to drinking water containing high levels of sulfate. In a population-based study of infants, episodes of diarrhea in a group of newborns exposed to sulfate from home tap water were examined. Recruitment, protocol, pilot study, and a self-administered questionaire are discussed. Also, an experimental trial of adult volunteers exposed to varying levels of sulfate in water was conducted. Methods used and results are discussed.