The changes of proto-oncogene c-fos and c-jun mRNA expression in angiotensin II (Ang II)-induced hypertrophy and effects of sodium tanshinone IIA sulfonate (STS) in the primary culture of neonatal rat cardiomyocytes were investigated. Twelve neonatal clean grade Wistar rats were selected. The cardiomyocytes were isolated, cultured and divided according to different treatments in the medium. The cardiomyocyte size was determined by phase contrast microscope, and the rate of protein synthesis was measured by [3H]-Leucine incorporation. The c-fos and c-jun mRNA expression in cardiomyocytes was detected by reverse transcription polymerase chain reaction (RT-PCR). It was found after cardiomyocytes were treated with Ang II for 30 min, the c-fos and c-jun mRNA expression in cardiomyocytes was increased significantly (P<0.01). After treatment with Ang II for 24 h, the rate of protein synthesis in Ang II group was significantly increased as compared with control group (P<0.01). After treatment with Ang II for 7 days, the size of cardiomyocytes in Ang II group was increased obviously as compared with control group (P<0.05). After pretreatment with STS or Valsartan before Ang II treatment, both of them could inhibit the above effects of Ang II (P<0.05 or P<0.01). It was suggested that STS could ameliorate Ang II-induced cardiomyocyte hypertrophy by inhibiting c-fos and c-jun mRNA expression and reducing protein synthesis rate of cardiomyocytes.