The purified wax fraction of the tubercle bacillus, which has been previously demonstrated as an essential element in causing delayed tuberculin hypersensitivity in response to the protein of the tubercle bacillus, is now found to have the same activity with regard to a simple chemical antigen, picryl chloride. One injection of this compound with wax intraperitoneally into guinea pigs results in a marked delayed cutaneous hypersensitivity, demonstrable by contact and intracutaneous test, and of long duration. The effect is not related to an adjuvant activity of the wax as defined by ordinary standards. The relationship of these observations to the occurrence of "heteroallergic" phenomena in tuberculosis is discussed. The possibility that the occurrence of spontaneous contact hypersensitivities may depend upon the presence of similarly active lipoidal components of the skin is commented upon.