Objective To study the inhibitory effect of cyclooxygenase 2 (COX 2) inhibitor celecoxib on the growth of hepatocellular carcinoma cell (HCC) line SMMC 7721 in vitro . Methods Growth suppression was evaluated by MTT method. Apoptosis related changes in morphology were observed by fluorescence microscopy (FM) and transmission electron microscopy (TEM). Apoptotic index (AI) was counted by the TDT mediated dUTP biotin nick end labeling (TUNEL) assay. The apoptotic rate was quantified by flow cytometry (FCM). Results Celecoxib inhibited the growth of HCC cells in a dose dependent manner. The growth inhibitory rates of HCC cells treated with 2, 10, 20, and 40 mmol/L celecoxib were 20.78%, 33.37%, 48 57%, and 64 96%, respectively ( P