AIM: To observe the role of endothelin antagonist bosentan that inhibits cultured neonatal mice cardiomyocyte from endothelin-1 (ET-1) induced cell hypertrophy. METHODS: Digested by trypsin, neonatal mice cardiomyocytes were isolated and cultured in 4 groups. With a group of regular culture cells as control, other three groups were respectively treated by bosentan 10 -8 mol?L -1, ET-1 10 -10 mol?L -1 andET-1 10 -10 mol?L -1+bosentan 10 -8 mol?L -1 which were initially administered to the culture medium. The cell growing was observed carefully through micrography. 72 hours later, the level of atrial natriuretic peptide (ANP) and ET-1 in the media of the 4 groups were determined by method of radioimmunoassay. RESULTS: The values of ANP in different groups were: 6.46? 0.38 ?g?L -1 in control, 4.87? 0.56 ?g?L -1 in bosentan group, 13.60? 1.12 ?g?L -1 in ET-1 group and 9.42? 0.58 ?g?L -1 in ET-1+bosentan group. Also by micrographic observation, endothelin induced cell hypertrophy was proved, and the hypertrophy could be reversed by bosentan. CONCLUSION: Endothelin induces hypertrophy of cultured neonatal mice cardiomyocytes, but it can be inhibited by endothelin antagonist of bosentan.