The structure of the capsular polysaccharide from Klebsiella type K38 has been reinvestigated. It is composed of pentasaccharide repeating units of the structure given below. In this structure, Sug stands for a 4-deoxy-threo-hex-4-enopyranosyluronic acid group, most probably having the beta-L configuration. H-1 NMR studies further indicate that this group assumes the H-1(2) conformation.