Apoptosis is a controlled form of cell death accompanied by distinct morphological and biochemical changes. In this study the nature of cytotoxicity induced by adriamycin (ADM) in rat thymocytes was evaluated. Morphological and biochemical changes characteristic of apoptosis were found to precede adriamycin-induced cell death. Our findings demonstrate the involvement of c-Myc, c-Jun, antioxidant enzymes CuZn superoxide dismutase and catalase, and perhaps poly ADP ribosylation in ADM-induced cell death.