Three bacterial strains, classified as Campylobacter jejuni biotype 1, Campylobacter coli, and NARTG (nalidixic-acid-resistant thermophilic Campylobacters), were tested for survival in water specimens kept at 4, 12, and 20°C. Five different water milieus were compared: sterile physiological saline, chlorinated tap water, dechlorinated tap water, polluted river water, and sterile filtered river water. With few exceptions, all organisms survived better at 4°C than at 12 or 20°C, regardless of the water milieu. Briefest survival was detected at 20°C; no viable Campylobacters could be demonstrated after more than 2 days at this temperature. Of the 5 waiter milieus tested, the highest mean survival time for all strains was obtained with dechlorinated tap water. In this medium, all 3 strains remained viable for 15 days at 4°C, 10 days at 12°C, and 2 days ait 20°C. Briefest survival was obtained in chlorinated tap water. Even residual amounts of Cl2 drastically reduced the survival of all strains tested. Only small variations in viability were detected for 2 of the strains tested after sterile filtration of a water source with a dense bacterial population. The results are discussed in relation to waterborne outbreaks of campylobacteriosis.