Summary: The changes of proto-oncogene c-fos and c-jun mRNA expression in angiotensin Ⅱ (Ang Ⅱ)-induced hypertrophy and effects of sodium tanshinone Ⅱ A 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