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Cell wall material was isolated from the pericarp of unripe and ripe tomatoes, free from intracellular compounds and active wall degrading enzymes. The wall preparations were sequentially extracted with cyclohexane-trans-1,2-diaminetetra-acetate (CDTA) at 20°, 0.05 M Na₂CO₃ at 1°, 0.05 M Na₂CO₃ at 20°, and 0.5, 1 and 4 M KOH at 20° to leave the α-cellulose residue, which contained a significant amount of pectic material. The polysaccharides isolated from the extracts were fractionated by anion-exchange chromatography and selected fractions were subjected to methylation analysis. The CDTA-soluble pectic polysaccharides had slightly-branched rhamnogalacturonan back-bones compared with the sodium carbonate-soluble pectic polysaccharides. The side chains of the pectic polysaccharides were mainly composed of β-(1→4)-Iinked galactopyranosyl and α-(1→5)-Iinked arabinofuranosyl residues, and …