The findings in 50 fine-needle aspiration biopsies obtained from 27 liver transplants in 24 patients were compared with concomitant histologic findings. When histology showed rejection, rejection was diagnosed in 20 out of 29 FNAB specimens; when rejection was absent histologically, FNAB was negative in 20 out of 21 specimens (sensitivity 69%, specificity 95%). There was a statistically significant correlation between the degree of immunoactivation as reflected by total corrected increment (TCI) in FNAB specimens and the portal triad cell density during rejection, while no correlation existed between the 2 parameters in situations other than rejection. When cholestasis was demonstrated histologically, FNAB showed cholestasis in 30 out of 31 specimens. Furthermore, FNAB showed fatty change in the hepatocytes in 29 out of 43 specimens from livers with histologically evident steatosis. Histology showed necrotic areas in 40 specimens; however, only in 12 concomitant FNAB specimens were necrotic clumps observed. In conclusion, FNAB is a good method for diagnosing acute liver transplant rejection as well as for evaluating intracellular cholestasis or fatty change. Furthermore, TCI seems to reflect the severity of cellular infiltration in the portal triads during rejection.