inserted dna fragments of nine clones lambda gt11 cenp 3 5 6 8 9 10 11 12 and 13 were found to be hybridized with the probe the same procedure was repeated for the remaining three clones using an inserted dna fragment derived from one clone i e lambda gt11 cenp 2 among the remaining three clones as the probe as the result the remaining two clones lambda gt11 cenp 4 and 7 were hybridized with the probe from these experiments it was found that the 13 clones can be divided into two groups a lambda gt11 cenp 1 3 5 6 8 9 10 11 12 and 13 and b lambda gt11 cenp 2 4 and 7 the inserted dna fragments of these groups were digested with various restriction enzymes and the cleaved dna fragments were subjected to agarose gel electrophoresis for size determination to obtain the restriction maps the inserted dna fragments of the a group were found to belong to the same group of cenp b gene which had been cloned previously by earnshaw et al earnshaw w c et al j cell biol 104 817 1987 while the restriction maps of the inserted dna fragments of the b group did not correspond to the cenp b gene of earnshaw et al and was thought to code other human centromere antigen the restriction.