In October 2001, the Wyoming Department of Health (WDH) was notified of six cases of acute gastroenteritis among persons who dined at a tourist restaurant in a historic mining community in central Wyoming. Additional cases were subsequently identified. A retrospective cohort study showed that consumption of the restaurant's tap water was associated with illness. Well water samples revealed the presence of fecal coliforms. Norovirus genogroup I was detected in three out of three stool samples and one well water sample.