After injection of ⁵¹Cr-labelled platelets, dogs were cooled down to 20 °C and rewarmed to 36 °C. Radioactivity increased over the hepatic area during cooling, to decrease again during rewarming. It increased continuously during the observation period over the splenic area. The inverse symmetry of the curves representing the radioactivity measured over the liver and in the peripheral blood together with the fact that splenectomy did not alter significantly the thrombocytopenia observed, strongly suggests that in the dog the liver is the main organ responsible for platelet sequestration during hypothermia.