Summary: The specificity of the immune deviation was studied by testing delayed, Arthus, and anaphylaxis hypersensitivity with hapten-carrier conjugates. Intravenous injections of high doses of carrier protein lowered delayed hypersensitivity to the carrier as well as antibodymediated hypersensitivity to the hapten, whereas the injection of high doses of homologous hapten-carrier conjugate also lowered delayed hypersensitivity to the carrier but did not affect the humoral reactions to the hapten.