Groupe Danone’s Research Center, Paris, France, and the Pasteur Institute, Paris, France, have undertaken a joint program to deepen scientific knowledge of the way probiotics work. This association, set up for an initial period of four years, is built on the complementary know-how of the two partners. The Groupe Danone Research Center has a unique collection of 3000 lactic ferments. Its research teams specialize in microbiology, biochemistry, fermentation biotechnology, immunology and human nutrition. The Pasteur Institute, internationally recognized for its expertise in microbiology and immunology, has developed in vitro and in vivo testing models with special relevance to probiotics. The teams working in partnership are focusing attention on ferments from the Danone collection, applying test methods developed by the Pasteur Institute. Results should allow the identification of new probiotic ferments and make for better understanding of their impact on human health.