Introduction The mammalian fetus presents cardiovascular adaptations to hypoxic stress. This response consists of bradycardia, increased systemic blood pressure and redistribution of cardiac output. This study describes the changes in cardiac output distribution in response to hypoxia in the chick embryo during development Method Fertilized eggs from day 9 to 19 of an incubation time of 21 days were opened at the air cell and a chorio-allantoic vein was catheterized. Two different labels of 15μ fluorescent microspheres were injected during normoxia and atthe end of 5 minutes of hypoxia. After the injections the embryos were sacrificed and the different organs were dissected and digested for microsphere isolation and subsequent fluorescent analysis Results We found a redistribution in favour of the heart and brain at the expense of the intestine, liver, yolk-sac and carcass Conclusion During hypoxia the cardiac output was distributed in favour of the vital organs similar to the mammalian fetus during hypoxia. This response seemed to develop with increasing incubation time