Louis Pasteur and Robert Koch: great scientists, national icons, opponents in the service of research. One is a Frenchman and chemist and is already in the second half of his life. He is honored worldwide with numerous prizes for his discovery of the rabies vaccine. The other was a still unknown German country doctor in his 30s, whose discovery of the tuberculosis bacillus was later awarded the Nobel Prize for Medicine. From 1881, the two were bitter rivals. Their 20-year rivalry resulted in spectacular progress in the fight against deadly epidemics.