Abstract: The cytotoxicity of cigarette smoke condensate(CSC) of 20 brands of domestic Virginia type cigarettes to Chinese hamster lung(CHL) mesothelial cells was tested with neutral red cytotoxicity assay, the results indicated that: 1) the IC₅₀ of chloroquine(positive control) was 15.0±0.23μg/mL, while the IC₅₀ of CSC of the 20 test brands ranged from 119.5±13.6 to 218.4±15.9μg/mL;2) the cytotoxicity of CSC with packet labeled tar of 15mg/cig.to CHL cells was significantly higher than those labeled tar of 11mg/cig, and extremely significantly higher than those labeled tar of 10, 9, 8, and 5mg/cig;and 3) the CSC negatively correlated with its IC₅₀ to CHL cells.