Abstract: In order to investigate the effects of exposure to cigarette smoke on the in vitro proliferation of human oral cell, Kentucky 3R4F reference cigarette was used as experimental cigarette and human oral epidermoid carcinoma cell line KB as experimental model. Cigarette smoke condensates (CSCs) were collected under ISO and Health Canada Intense (HCI) smoking regimes for the exposure assessment of human oral cells, the effects of CSCs on the metabolic activity and nucleic acid replication activity of the cells were assessed, and further analyzed versus the release levels of main harmful components in total particulate matter (TPM) of mainstream cigarette smoke. The results indicated that: 1) CSCs exposure inhibited the in vitro proliferation of oral cells and imparted certain toxicity to their metabolic activity and nucleic acid replication activity. 2)Under HCI smoking regime, the release of harmful components per unit TPM and per unit nicotine in mainstream smoke of 3R4F reference cigarette was lower and the moisture content in CSCs was higher than those under ISO regime; these two factors explained the lower cytotoxicity of HCI regime CSCs.