[en] The propagation of Escherichia Coli (ATCC 11229, Gelsenkirchen) is compared with that of conservative tracers in groundwater. The experiments were performed with injection quantities of 10₇, 10₈, 10₁₀ and 10₁₁ of Escherichia Coli. Both, bacteria and conservative tracers pass their maximum at the same instant in the observation gauges. With injection quantities of more than 10₈, the propagation of the Escherichia Coli sets in at the same time as it begins with the dyes. When the quantities range below 10₈, the propagation begins after that of conservative tracers, because Coli bacteria were measured with a lower degree of detecting sensitivity than the tracers. With Coli injection quantities ranging above 10₁₀, an increased filtering of these bacteria can be observed. Coli bacteria propagate more laterally than conservative tracers, however it could not be proved that this lateral propagation depends on the bacteria concentration. (orig.)