AIM: To evaluate the different conditions inducing mouse embryonic stem cells (ESC) in vitro to differentiate into cardiomyocytes. METHODS: BRL conditioned medium was used to promote the growth of ESC and maintain them in an undifferentiated state. During the inducing process, retinoic acid (RA), DMSO, activin-A and TGF-? 1 were used as inducing reagents, and made up six kinds of differentiating medium. Then a three-step method inducing ESC cultured in hanging drops, in suspension and in plating was used to induce the differentiation of ESC. RESULTS: ESC were induced in vitro to differentiate into cardiomyocytes. Of all groups, the highest differentiating rate was observed in the group induced by activin-A (20 ?g/L) and TGF-? 1 (2 ?g/L). CONCLUSION: The inducing conditions including activin-A (20 ?g/L) and TGF-? 1 (2 ?g/L) is very valuable in inducing ESC differentiation into cardiomyocytes. [