OBJECTIVE To evaluate the application of RNA interference in the study of latent membrane protein-1 (LMP-1) in EB virus-positive nasopharyngeal carcinoma (NPC) cell line C611. Observe the effects of LMP-1 silencing on NPC cell growth. METHODS Four synthesized small interference RNA (siRNA) were transfected into NPC cell using Oligofectamine reagent. LMP-1 mRNA level was determined by semi-quantitative reverse transcriptase polymerase chain reaction (RT-PCR). Flow cytometry and MTT assay were employed to analyze the effects on cell cycle and proliferation. RESULTS The most effective sequence found out among the 4 candidates. Single dose of this siRNA caused nearly 90% loss of LMP-1 mRNA in C611 cell. The specific inhibition could last for 96 hours if re-transfection was preformed. LMP-1 siRNA treatment resulted in cell cycle arrest at G0-G1 stage in C611, accompany with a reduction of cell proliferation by 32.9%. While EBV-negative NPC cells appeared unaffected. CONCLUSIONS These results provided solid testimony that EBV-encoded latent membrane protein-1 was vulnerable to RNA interference and, selective inhibition of LMP-1 had anti-proliferation effect on NPC cell. RNA interference could be a powerful tool in further investigations of LMP-1 and a novel therapeutic strategy for EBV-related NPC patients.