Galactomannans isolated from the seeds ofGleditsia macracantha (GMM) andGleditsia texana (GMT) have molecular masses (MM) of 750.000 and 795.000 and galactose to mannose ratios of 1.0∶4.9 and 1.0∶3.8, respectively. GMT and GMM are depolymerized to fragments of MM 25 and 19 kDa with retention of the primary structure and are studied by13C NMR spectroscopy. The principal chains of GMM and GMT are β-1-4-mannopyranose residues in which the hydroxyl groups of C-6 are substituted by single α-D-galactopyranose units.