In July 1984, an outbreak of gastroenteritis occurred in a suburban community in Texas. A random telephone survey of 100 of 1791 households in the community identified an attack rate of 34%. The outbreak was traced to contamination of the community water supply, an artesian well. Fecal coliforms were identified in untreated drinking water from the well during July. Stool examinations and serologic tests identified Cryptosporidium as the etiologic agent. Cryptosporidium should be added to the list of waterborne organisms capable of causing outbreaks of gastroenteritis.