New antibiotics, agglomerins A, B, C and D, were isolated from the culture broth of a bacterial strain identified as Enterobacter agglomerans. These antibiotics are acidic in nature and their sodium salts are obtained as colorless crystalline powders, soluble in lower alcohols. All the antibiotics shows characteristic UV maxima at 248 and 298 nm. Molecular formulas: A, C15H21O4Na; B, C17H23O4Na; C, C17H25O4Na and D, C19H27O4Na; were indicated by elemental analysis and MS. These antibiotics are active against a wide variety of anaerobic bacteria and weakly against aerobic Gram-positive bacteria in vitro.