We studied the characteristics of the pulmonary reimplantation response (PRR) in single-lung transplantation (SLT), and detailed the occurrence, evolution, prognosis and risk factors of this complication. Forty single-lung transplant recipients were studied. Twenty four patients developed hypoxaemia and allograft infiltrates consistent with the PRR. In 40% of the cases hypoxaemia was severe, precluding weaning and requiring prolonged mechanical ventilation with high fractional inspiratory oxygen (FIO2). The mean duration of ventilation was 7 days (range 1-19 days). Clearing of the chest radiographs was progressive, with complete resolution between 6 and 21 days. In all cases, the pulmonary arterial wedge pressure was normal (6 +/- 2 mmHg) suggesting low pressure oedema. Sampling of the pulmonary oedema fluid revealed that the ratio of protein concentration in oedema fluid to that in serum exceeded 0.5. In patients with severe PRR (40% of cases) clinical, radiographic and haemodynamic abnormalities were identical to adult respiratory distress syndrome (ARDS), but the prognosis was more favourable with no death directly related to PRR in our patients. The mean duration of graft ischaemia of the oedematous grafts (241 +/- 103 min) was significantly longer than that of nonoedematous grafts (155 +/- 71 min). These date suggest that prolongation of graft ischaemia increased the incidence of PRR.