In June 1987, an outbreak of acute enteritis occurred over a period of 2 weeks in a small rural community where the potable water supply is unfiltrated and unchlorinated. Campylobacter jejuni was isolated from 6 patients. A case-control study performed in a local fiberglass shop where workers drink a lot of water, showed an association between the occurrence of enteritis and the consumption of 10 or more 8-ounce glasses of water per day (Odds Ratio = 6, p = 0.04). The attack rate of enteritis was 23.2% (13/56) in that industry where a dose response relationship was also noted (p = 0.05). C. jejuni was not recovered from the local water supply, which had temporarily been chlorinated the day before the samples were drawn. However, samples taken just before the outbreak showed high coliform counts. This episode suggests that unprotected water systems may be contaminated by C. jejuni.