BACKGROUND To elucidate the pattern and mechanism of cisplatin-induced apoptosis and its role in tumor chemotherapy. METHODS Apoptosis induced by cisplatin in human lung adenocarcinoma cell line A549 was detected by cell morphology, agarose gel electrophoresis, DNA-end-labeling and flow cytometry analysis techniques. RESULTS Cisplatin-induced apoptosis of A549 cells persisted and augmented gradually from 12 to 72 hours after treated with 3 mg/L cisplatin. All of A549 cells treated respectively with 1, 3, 5 and 7 mg/L cisplatin showed apoptosis. Apoptotic effects increased in a time-dependent pattern and a concentration-dependent pattern. A549 cells were blocked in G1 phase after treated with cisplatin. CONCLUSIONS Induction of cell apoptosis may be an important mechanism of anti-tumor efficacy of cisplatin.