The centromere position was shown to be located in the middle of the short eucromatic portion of the marked acrocentric chromosomes of primates. The marked metacentrics of primates may have originated through processes of centric fusion involving 1 pair of marked acrocentrics and another pair of autosomes. In the marked metacentrics of primates, the short eucromatic portion of the marked arms corresponds to about 1/2 size of the short eucromatic portion of the marked acrocentrics. This characteristic is consistent with the location of the centromere and the hypothesis of centric fusion as the origin of the marked metacentrics of primates.