Eleven acute rejections were found in 9 patients with liver transplantation due to end-stage liver cirrhosis. The rejections were diagnosed with fine-needle aspiration biopsy (FNAB) giving the cellular picture of immunoactivation in the liver graft when compared to a simultaneous sample of peripheral blood. s-Alkaline phosphatase and s-bilirubin increased within 1 week after onset of rejection in 7 and 10 cases, respectively. s-Alanine amino-transferase and b-ammonium were of no value in the diagnosis of acute rejection. A core biopsy was obtained only in a case of severe liver damage, mainly to estimate the need for retransplantation. One year after grafting, 6 out of 7 cirrhotic patients are well, all with normal liver function. Two have died of sepsis. One patient died from pulmonary metastases of occult liver carcinoma 6 months after the transplantation. FNAB seems helpful in detecting early acute rejection and also excluding such an event in the liver graft.