To investigate the properties and functions of telomere in cells resistant to cadmium and adriamycin, changes of telomeric band number were studied using fluorescence in situ hybridization (FISH) technique. To determine the amplification of telomeric signal, we counted total number of telomeric bands, number of marker chromosomes and number of double minutes(DMs) in cadmium resistant and adriamycin resistant cell groups. Cell lines exposed to cadmium showed higher ITB scores than controls. Cell line with longest exposure to cadmium had the highest ITBs. Adriamycin resistant cell lines showed lower ITB scores than controls. Number of marker chromosomes in cadmium resistant cell lines was similar to that in control cells whereas that in adriamycin resistant cell lines was decreased. Total number of DMs with presence of telomere signal was increased in cadmium resistant CHO cells, whereas no increase was found in adriamycin resistant cells. Our results suggest that there bight be different mechanisms in the acquisition of resistance to different agents.