Abstract: We examined the chromosomal basic protein from the Dinoflagellate Amphidinium carterae.The chromosomal basic protein of A.carterae and calf thymus histones as control were isolated by flur steps:Methanol-fixation,cell-homogenization,0.3N HCI-extraction and acetone-sedimentation.The qualitative examination of the isolated proteins was made in acid urea polyacrylamide gel electrophoretic system.As a result,the histones from calf thymus were separated into five bands:H1,H3,H2A,H2B and H4,and no other protein bands were observed.The extracted protein from A.carterae showed only one single band.Its electrophoretic mobility was similar to that of calf thymus histone H4.This result together with those of other authors on biochemical and cytochemical studies all indicates that the chromosomes of dinoflagellate contain chromosomal basic protein.The opinion that the lack of chromosomal basic proteins is an important character of dinoflagellate seems to be incorrect.