Sugarcane (Saccharum spp. hybrids) has great potential to provide feedstock to a biofuel industry in the United States. Sucrose from sugarcane can easily be fermented into ethanol. Sugarcane and related species also yield large amounts of biomass that would be suitable for conversion to biofuel. There is limited information on the composition of the biomass from sugarcane. This study was done to determine the cell wall composition of the residue left after expressing the juice from the stalks of a sample of different Saccharum genotypes. Ninety-six Saccharum genotypes representing commercial cultivars and wild species were grown in cans during the spring and summer of 2006. In August 2006, plants were harvested by cutting at soil level. Plant material was chipped, and juice was expressed from a 1000-g sample. The remaining fiber cake was dried, and then ground through a 1 mm screen. Cell wall composition was determined on duplicate 0.5 g samples by sequential extraction using neutral detergent (NDF), acid detergent (ADF), and 72% H₂SO₄ (ADL). Remaining residue was then ashed. The composition of the fiber cakes ranged from 8 to 22% soluble material, 28 to 35% hemicellulose, 40 to 52% cellulose, and 7 to 14% lignin. This is lower than some earlier reports of lignin content in sugarcane bagasse, possibly due to the ADL method used to determine lignin, which underestimates lignin in grasses.