The tannin composition of wood of Ceratonia siliqua (carob) was studied using GC-MS and classical chemical assays. Aqueous methanolic extracts of carob heartwood and sapwood were fractionated using organic solvents of increasing polarity, and GC-MS analyses were performed before and after hydrolysis. Prior to hydrolysis, gallic acid, catechin and its derivatives, methyl inositol and chalcone were determined as the major compounds found in the free form. Aqueous fractions of both wood types were hydrolysed with hydrochloric acid in methanol and extracted with organic solvents and water. These fractions were rich in methyl inositol, gallic acid, glucose and other monosaccharides. The results show that carob wood contains predominantly gallotannins and proanthocyanidins. The technique employed is shown to be a valuable tool and an alternative method to HPLC determination of hydrolysable tannin composition. Copyright (C) 2004 John Wiley Sons, Ltd.