Campylobacter jejuni (C. jejuni) has not been found by us in raw sewage or anaerobically stabilized sludge. Therefore the survival of C. jejuni has been tested in drinking water, river water and sewage. A suspension of about 10(7) C. jejuni per ml was filled into dialysis tubes which were placed in wire baskets and exposed. Exposition to drinking water was done using two continuously perfused containers in the laboratory, whereas exposition to sewage and river-water was performed at the local sewage treatment plant. Viable C. jejuni numbers per ml were reduced to zero in drinking water during five days starting from 10(6)/ml, in about two days in river water, starting from 10(8)/ml, and one and a half day in untreated sewage, starting from 10(7)/ml. E. coli showed no significant reduction in any of the experiments. Survival of C. jejuni in water seems to be restricted to a few days. The concentration of oxygen or nutrients in the water seems to be without relevance, whereas the most significant variable is temperature, which in our experiments was highest in the sewage and lowest in the drinking water containers.