The leukocyte migration inhibition test in agarose medium was performed in 23 cases of clinically diagnosed drug-induced hepatitis. When the test antigen was the combination of soluble phase of a liver homogenate fractionated by Sephadex G-100 which should have contained liver specific antigen and the offending drug the leukocyte migration was inhibited in 86% of cases. Whereas none of 12 cases of drug allergy without hepatic injury showed a positive result with the same combination of antigens. Other organ homogenate-muscle and kidney-never gave positive results when mixed with the offending drugs in cases of drug-induced hepatitis. It was concluded that in hypersensitivity type drug-induced hepatitis cell-mediated immunity might be established to the complex of liver specific antigen and the drug.