Morphine is not only an analgesic treating pain for patients with cancer but also a potential anticancerdrug inhibiting tumor growth and proliferation. To gain better insight into the involvement of morphine inthe biological characteristics of gastric cancer, we investigated effects on progression of gastric carcinoma cellsand the expression of some apoptosis-related genes including caspase-9, caspase-3, survivin and NF-κB usingthe MGC-803 human gastric cancer cell line. The viability of cells was assessed by MTT assay, proliferation bycolony formation assay, cell cycle progression and apoptosis by flow cytometry and ultrastructural alteration bytransmission electron microscopy. The influences of morphine on caspase-9, caspase-3, survivin and NF-κB wereevaluated by semi-quantitative RT-PCR and Western blot. Our data showed that morphine could significantlyinhibit cell growth and proliferation and cause cell cycle arrest in the G2/M phase. MGC-803 cells which wereincubated with morphine also had a higher apoptotic rate than control cells. Morphine also led to morphologicalchanges of gastric cancer cells. The mechanism of morphine inhibiting gastric cancer progression in vitro mightbe associated with activation of caspase-9 and caspase-3 and inhibition of survivin and NF-κB.