Some chromosomal or subchromosomal deletions observed in a variety of cancer cells may be related with metastatic properties of the tumor cells. Thus, relationship between allelic losses and metastatic ability is here investigated of ten in vitro clones obtained from 505 cells that are derived from a fibrosarcoma induced in a F1 mouse between C3H and C57BL strains. Allelic loss was examined using 61 microsatellite markers spanning all autosomes and deletions of various loci were observed in all of the clones. One clone showed a metastatic ability higher than the parental 505 cells and the other clones. This particular clone specifically lost a chromosome 16 derived from C57BL, suggesting an association of this chromosome deletion with the metastatic ability. Consistently, examination of metastatic nodules derived from 505 cells and one in vitro clone showed that the cells with deletion of the C57BL chromosome increased in number during metastasis. These results suggest that mouse chromosome 16 may harbor a gene(s) involved in metastasis.