The β polypeptide chain of adult hemoglobin prepared from the rhesus monkey(Macaca mulatta)was digested with trypsin. All the tryptic peptides thus obtained were isolated and purified by column chromatography and paper chromatography, and then the amino acid sequence in these peptides was determined. Comparisons of the results with the known sequences of the corresponding peptides from adult human hemoglobin showed there were differences at eight positions in the amino acid sequences of the seven peptides