The Gram-negative bacterium Pseudomonas solunacearum is responsible for causing wilt diseases in a wide range of hosts which extend to more than 400 plant species belonging to 30 different botanic families' of economic importance to agriculture. It has been suggested* that the lipopolysaccharide present as the major outer-membrane component of the Gram-negative bacterium plays an important role in the host-pathogen interaction. Recently, the chemical analysis of the lipopolysaccharide (LPS) of P. solanacearum biotype II has been reported3. In this communication, we report the structure of the purified polysaccharide part of the LPS isolated from a virulent strain (ICMP 9758) of P. solanaceurum. P. sofanacearum ICMP 9758 was grown at 37ยฐC in tryptose-tryptone medium and the LPS was extracted by using the hot phenol-water method4. The LPS was cleaved with dilute acetic acid and the polysaccharide fraction, isolated by gel-permeation chromatography, had [(Y],, + 21" (c 1.5, H20). Quantitative sugar analysis by GLC showed that the polysaccharide contained rhamnose and glucose in the molar ratio 2: 1 (the author of ref 3 regrets the incorrect reporting of the amounts of constituent sugars of the polysaccharide). The specific rotations of the sugar monomers, isolated from the polysaccharide hydrolysate by preparative paper chromatography, enabled us to assign the D configuration to the glucose, and the L configuration to the rhamnose residues. The r3C NMR spectrum of the polysaccharide showed three prominent signals for anomeric carbons at 101.6, 100.3, and 99.4 ppm with 'Jou values of 169, 170, and 172 Hz, respectively, indicating the anomeric configurations of the three component sugars to be o. The absence of signals from the region 82-88 ppm proved that all the residues were pyranoid. The calculation of the specific optical rotation of the polysaccharide ( + 15") by Klyne's