Cellulose contents were estimated in 12 seaweed samples belonging to different families e.g. red, brown and green, growing in Indian waters. Each cellulose sample was fractionated to yield alpha (alpha) and beta (beta) celluloses. Characterization was done using various analytical tools and results were validated by comparison with those of the cellulose obtained from Whatman filter paper No. 4. The greatest yields of cellulose (crude), alpha- and beta-cellulose were obtained from Gelidiella acerosa (13.65%), Chamaedoris auriculata (9.0%) and G. acerosa (3.10%). G. acerosa was also found to contain relatively high amount of alpha-cellulose (8.19%). The lowest cellulose contents were recorded from Kappaphycus alvarezii (2.00%) and Sarconema scinaioides (2.1%), while the latter contained the lowest alpha-, and beta-celluloses (1.0% and 0.30%, respectively). It appears that agarophytic and alginophytic algae contain high cellulose and alpha-cellulose contents, while the carrageenophyte contains low cellulose. The brown algae, in general contain high cellulose as well as alpha- and beta-celluloses. (C) 2009 Elsevier Ltd. All rights reserved.