The growth in present of bile is a key reaction for differentiation of gramnegative anaerobe non-spore-forming bacilli, especally for species of bile-resistent genus Bacteroides and bile-sensitive genera Porphyromonas and Prevotella. A methode for determination of bile-sensitivity is the use of bile-impregnated filter paper disks on enriched, nonselective media, which allow growth even species with high requirements for growth. The use of bile is associated with disadvantages because of its instable composition and its high viscosity making accurate dosage difficult. The bile-sensitivity was determined on 316 strains of gramnegative anaerobe non-spore-forming bacilli (120 bile-resistent Bacteroides, Fusobacterium; 196 bile-sensitive Porphyromonas, Prevotella, Bacteroides, Fusobacterium) with sodium cholate, sodium desoxycholate und sodium taurocholate in comparison to bile. Bile acids are the most antimicrobial effective components of the bile, chemical defined, and well to dose. The concentrations per disk for the sodium bile acids were 1, 5, and 10 mg, for the bile 20, and 25 mg. For the two concentrations of the bile the results were similar to these found in literature. Because of its small antimicrobial activity sodium taurocholate is not appropriate. Similar results as bile were demonstrated by sodium desoxycholate and sodium cholate, each with the 10 mg concentration. Due to better handling, greater halos, and better differentiation of the Fusobacterium species, sodium cholate is appropriate for determination of bile-sensitivity. Therefore strains with a zone of inhibition > 15 mm in diameter are considered to be bile-sensitive, for Fusobacterium species alternatively > 13 mm. The results should be acquired at the latest 48 hours after beginning of incubation. The importance of testing the bile-sensitivity was demonstrated by comparison the results with two commercial kits (Rapid ANA II and BBL Crystal) for the species P. heparinolytica and B. uniformis.