Cell wall composition and structure were examined in visually normal (N), granulated (G), and collapsed (VC) juice vesicles of `Marsh Seedless' grapefruit (Citrus paradisi) Macf.). According to gel-filtration data, VC appeared to be associated with a modification of water-soluble (WSP) and chelate-soluble (CSP) pectin molecular weight (Mr); small-Mr pectins increased, whereas large-J4. pectins decreased. The difference in M= of pectins did not appear to be mediated by polygalacturonases. Molecular weight of hemicelluloses did not differ. Granulated vesicles contained about two times more structural polysaccharides (pectins, hemicelhdose, and cellulose) than N vesicles, although hemicellulose and pectin M= modification were absent. Ion-exchange profiles of WSP, CSP, and hemicelhrlose fractions of VC and G vesicles were not different from those of N vesicles. Individual cells in vesicles with G and these vesicles themselves were much larger than those of N vesicles, whereas cells in VC were partially or completely collapsed.