A grass carp （Ctenopharyngodon idellus）cell culture ZC7901 was used as an in vitro model system to study the effect of heavy metal ions on fish cells. The results showed that the cell culture chemically stressed by six heavy metal ions, Cd²⁺，Cr⁶⁺，Hg²⁺，Cu²⁺，As⁵⁺ and Pb²⁺, exhibited cell death accompanied by various morphological alterations such as nuclear condensation, chromatin abutted sharply against nuclear membrane and developed into distinct apoptotic-like bodies, which were characteristic features seen in apoptosis. By agarose gel electrophoresis, DNA ladder were clearly visualized, which indicated the specific degradation of DNA. Also terminal-deoxynucleotidyl transferase mediated dUTP nick end labeling (TUNEL) analysis of the cells demonstrated DNA fragmentation localized in the dying cells as well as in the additional apoptotic-like bodies. All the results indicated that six heavy metal ions, Cd²⁺，Cr⁶⁺，Hg²⁺，Cu^{2+，As5+ and Pb2+, were all able to induce apoptosis in fish cells.}