Strains of Anaerovibrio lipolytica isolated from sheep- and cow-rumen contents on a linseed oil -- rumen fluid -- agar medium fermented ribose, glycerol and DL-lactate. Fermentation products from glycerol were propionate and succinate, while ribose, fructose and DL-lactate were fermented mainly to acetate, propionate and carbon dioxide. Propionate is formed in this organism by the dicarboxylic acid pathway similarly as in propionibacteria. Measurements of the rate of lipolysis by pure cultures suggest that the organism may play an important role in the lipolytic activity of rumen contents of sheep. The demonstrated fact that the cell-free lipase excreted in the culture medium can easily be adsorbed on particulate matter in autoclaved rumen fluid may explain the absence of free lipase in clarified rumen liquor.