Vascular resistance was determined in 40 kidneys after preservation in Collins' or Sacks' solution for 24 and 48 hours. Kidneys without warm ischaemia and kidneys with up to 60 min of warm ischaemia prior to preservation were investigated, vascular resistance was determined during short time perfusion with Tis-U-Sol at 4 degrees. The experiments showed that cold preservation of kidneys with no warm ischaemia or 15 min of warm ischaemia gave a small increase in vascular resistance, independent of the solution used. 30 and 60 min of warm ischaemia gave a considerable increase in vascular resistance, but less increase was found in kidneys preserved in Sacks' solution. Determination of the weights and thereby formation of oedema showed slight dehydration in kidneys preserved in Sacks' solution. Kidneys preserved in Collins' solution showed small increase in weight. No correlation was, however, found between the vascular resistance and degree of oedema.