Three different procedures for isolation of cellulose from sugarcane bagasse (SCB) were comparatively studied. Sequential extractions of dewaxed SCB with water with or without ultrasonic irradiation, various concentrations of alkali and alkaline peroxide yielded 44.7 and 45.9% cellulose preparations, which contained 6.0 and 7.2% associated hemicelluloses and 3.4 and 3.9% bound lignin, respectively. Delignification with acidic sodium chlorite followed by extraction with alkali (10% KOH and 10% NaOH) gave cellulose yields of 44.7 and 44.2%, which contained 5.7 and 3.7% residual hemicelluloses and 1.6 and 1.5% remaining lignin, respectively. Interestingly, a one-step treatment of SCB with an 80% acetic acid–70% nitric acid mixture under the conditions given yielded 43.0–43.6% of the more pure cellulose fractions, which contained minor amounts of bound hemicelluloses (3.2–4.3%) and were relatively free of associated lignin (0.2–0.6%). The isolated six cellulose samples were comparatively studied by both degraded methods such as acid hydrolysis and thermal analysis and non-degradation techniques such as FT-IR and CP/MAS 13C-NMR spectroscopy, and the relative crystallinity was also comparatively estimated.