in vitrotests of cell-mediated immunity were performed using blood obtained from subjects with unexplained hepatitis following halothane anesthesia to determine whether sensitization to potentially antigenic products of halothane metabolism might exist. Both lymphocyte transformation and leukocyte migration-inhibition tests were undertaken in the presence of trifluoroacetylated human liver specific protein and trifluoroacetylated human serum albumin. All tests in the presence of these potential antigenic complexes were negative. The results support the view that cell-mediated hypersensitivity to trifluoroacetylated proteins does not contribute to the pathogenesis of hepatic dysfunction following halothane anesthesia