Cardiomyogenesis, a cardiac cell formation, includes differentiation, proliferation and migration of early cardiomyocytes. In vitro, mature cardiomyocytes are characterized by spontaneous beating and expression of cardiac-specific genes. Interestingly, under pathological conditions such as heart ischemia an activation of fetal gene expression connected with reactivation of cardiomyogenic process is reported. This effect is suggested to help the cardiac tissues to adapt to stress conditions. Cardiomyogenesis is regulated by a large number of factors including oxygen availability. Hypoxic conditions, which are characteristic for early embryonic development, lead to stabilization of hypoxia inducible factor 1 alpha. However, role of HIF-1alpha in regulation of cardiomyocyte differentiation is not well understood. With aim to better understand the role of HIF-1alpha within cardiomyocyte development and reprograming, cardiomyogenesis in wild type and HIF-1alpha depleted murine embryonic stem cells was analyzed in vitro. The level of expression of individual cardiospecific genes was significantly lower in HIF-1alpha deficient cell line compared to wild type cells after induction of cardiomyogenesis in vitro. This suggests lower number of progenitor cells to enter cardiomyogenesis in these HIF-1alpha deficient cells. However, despite this effect, cells which have already entered the cardiomyogenic process are similar in both wild type and HIF-1alpha deficient line. They both start to beat at the same time after the onset of differentiation and their beating characteristic is comparable. Moreover, they have a similar morphology. Thus, although HIF-1alpha is important for induction of development of cardiomyogenic progenitors HIF-1alpha had no significant effect on cardiomyocyte maturation in in vitro culture.