A high priority in organ transplantation research is to increase the number of hours that an organ can be successfully preserved. Transplant programmes rely on hypothermia and flush solutions to maintain organ viability during the storage period. We studied long-term morphology in lungs stored for 24 or 48 hours using two modified versions of University of Wisconsin solution, one mimicking the extracellular medium and the other the intracellular medium. Four weeks after transplantation, X-ray and angiograms were used to assess the proportion of ventilating tissue, and light and electron microscopy to analyse morphology. Pulmonary tissue presented near-normal histological appearance in well preserved areas while fibrosis and chronic inflammation were found in scarring processes. Electron microscopy studies revealed some damage-related changes in tissue which appeared histologically normal. Four weeks after transplantation, quality and quantity of recovery were uniform for both solutions tested after 24 hours of storage. However, without reaching significance, after 48 hours the quantity of successfully preserved pulmonary tissue was greater in the group stored in the intracellular solution.