Vascular resistance was determined in 40 rabbit kidneys after graded warm ischaemia up to 60 minutes and preservation in Collins' solution for 24 and 48 hours. Half of the animals were treated with chlorpromazine 3.5 mg/kg before induction of the ischaemia. Vascular function was determined during short-term perfusion with TIS-U-SOL at 4 degrees C. The experiments showed that warm ischaemia of 30 and 60 minutes duration gave an increase in vascular resistance. The increase was, however, smaller in kidneys pretreated with chlorpromazine. Preservation in Collins' solution for 24 and 48 hours did not change this correlation. Determination of the weights and thereby formation of oedema showed that all kidneys preserved had a small increase in weight. No difference was found between pretreated kidneys and untreated kidneys. It is concluded that pretreatment with chlorpromazine is capable of diminishing vascular contraction during the warm ischaemic period and that preservation in Collins' solution for up to 48 hours does not alter this beneficial effect.