Abstract: AIM: To examine the effect of atorvastatin on p21 expression of left ventricular hypertrophy in spontaneously hypertensive rats( SHR) and the underlying mechanisms of atorvastatin in alleviating myocardial hypertrophy. METHODS: Sixteen 8-week-old male SHR were randomly divided into ATV group( n = 8) and SHR group( n = 8). Age-matched Wistar-Kyoto rats served as normotensive control group( WKY group,n = 8). In ATV group,atorvastatin was given at a dose of 50 mg / kg per day by gastric gavage. In the SHR group and WKY group,the same volume of distilled water was given. Blood pressure was measured every 2 weeks and after 10 weeks,plasma lipid levels were measured. Ventricular weight index was calculated by the ratio of left ventricular weight to body weight and p21 expressions were examined by immunohistochemistry analysis and RT-PCR. RESULTS: No significant difference was found in plasma lipid levels and blood pressure between ATV group and SHR group. Compared with that in the SHR group,left ventricular weight index decreased significantly in the ATV group( P < 0. 01) and the myocardium p21 expression increased significantly( P < 0. 01). The expression of p21 mRNA in cardiomyocytes were negatively correlated with HW / BW( r =-0. 709,P < 0. 01) and LVW / BW( r =-0. 665,P < 0. 01). CONCLUSION: Atorvastatin increases myocardium P21 expression and alleviates left ventricular hypertrophy in spontaneously hypertensive rats.