Abstract: A microbial process for detection of toxic substances. The bacterial luminescence test so far used to detect toxic substances is extremely fast in its performance and reacts with very high sensitivity to heavy metals such as mercury and lead. However, that is not the case for other toxicologically relevant heavy metals such as cadmium and chromium. The inhibitory effect of toxic substances on the phosphotransferase system of bacteria, in particular, the E. coli mutant 1219 bgl+, is set forth as proof for the presence of toxic substances in samples. This test method responds with high sensitivity to the presence of the heavy metals cadmium and chromium. The test process constitutes a complement to the bacterial luminescence test and makes it possible to quickly exclude the presence of toxicologically relevant concentrations of cadmium and chromium in such cases where only a slight or no effect at all is indicated on the phosphotransferase system.