The complete sequence of 125 amino acid residues (molecular weight, 13, 775) in the calf thymus histone rich in lysine and serine was established by overlapping into a unique sequence of the complete or partial sequences of tryptic, chymotryptic, and thermolysin peptides revealed in the preceding papers. This complete sequence was further confirmed by analyses for the N- and C-terminal sequences, and especially by fragmentation at two methionine residues with cyanogen bromide. The establishedsequence was characterized in comparison with one complete and two partial sequences of other types of histone. Thus it was revealed as characteristics common to the Jiistone sequences that either terminal region (N-terminal in this case) is the most enriched in basic amino acids and proline with characteristic clustering of basic residues and short spacing between them, whereas the other regions are enriched in hydrophobic, acidic, and hydroxyamino acids with depletion in basic residues and long spacing between them. Based on these common features of the various sequences and the reported conformational changes of this and other histones, a molecular model of histone-DNA complex was proposed which illustrates the composition and structure of native deoxyribonucleoprotein and indicates the mechanisms responsible for constraining the DNA into superhelix and thus regulating its template activity for RNA synthesis.