We have isolated and characterized several highly repetitive DNA elements from two species of Chinese bitterlings, Rhodeus atremius suigensis and R. ocellatus ocellatus. They comprise a partly interspersed and partly tandem repetitive family of about 1.0 to 1.3 kb in length. Individual elements showed considerable length variation, but genomic Southern blotting revealed two major length groups. Their restricted presence of these elements among related species and relative copy number differences indicated rapid change of genome structure in this group of fish. The isolated elements may be useful landmarks for further chromosomal studies.