Animals with long necks, where the brain may be situated more than a meter above heart level, have high arterial blood pressures to maintain adequate cerebral perfusion. In both giraffes and ostriches, the tallest living mammals and birds on the earth today, the pressure in the carotid arteries declines with the vertical distance above the heart according to gravity, and results in a normal inflow pressure at the brain. In anaesthetised giraffes and ostriches, the pressure generated by the heart is reduced when the head is lowered below heart level, which may be an important mechanism protecting the brain. In both animals, a large volume of blood also pools within the jugular vein when the head is lowered and this seems to reduce cardiac filling and hence ventricular pressure development on the giraffe heart, but a similar mechanism does not appear to apply to the ostriches. In line with these observations, arterial pressure of giraffes is exquisitely sensitive to volume depletion by bleeding, while the ostrich is less affected. Surprisingly, the relative mass of giraffe heart is not bigger than other mammals, and we believe that its capacity to generate high pressures resides with relatively small end-diastolic and end-systolic volumes providing a normal mammalian wall tension. This may entail an evolutionary scenario where the ability to generate high blood pressures has evolved at the expense of a reduction in cardiac output.