A "capillary leak" syndrome resulting from cyclosporine-induced membrane toxicity has been postulated as the cause of convulsions and pulmonary edema in bone marrow transplant recipients. We describe here the occurrence of similar complications in a group of 21 adults receiving liver transplants since July 1982. Of 12 patients treated with i.v. cyclosporine (4 mg/kg/day), 2 developed an adult respiratory distress syndrome (ARDS) within five days of the operation, but it was not found in those given prednisolone (0.05-1.0 mg/kg/day) and azathioprine (1.0 mg/kg/day). ARDS only occurred when cyclosporine was administered through a central vein, and therefore might be related to high concentrations of cyclosporine reaching the pulmonary circulation and causing damage to vascular membranes. Convulsions occurred in one patient given i.v. cyclosporine, and in three when therapy was changed and cyclosporine and corticosteroids were used in combination. Convulsions did not occur inthe same patients as ARDS, were not part of a generalized "capillary leak" syndrome, and were not associated with hypertension or renal failure, as reported elsewhere in children. Fluid retention consequent on cyclosporine administration aggravated by the use of corticosteroids appears to be the most likely explanation of the convulsions.