INVESTIGATIONS into taste sensitivity for bitter as a particular hereditary characteristic in man have found their practical application in human, that is, population genetics. Phenylthiocarbamide (PTC) has been found the most reliable among the bitter substances used for discrimination between sensitive persons and insensitive. We believe that of the different methods described^{1â 3} the most advantageous one is that of Harris and Kalmus^{4â 7}. In addition to the testing and checking of modes of heredity, the establishment of frequency of tasters and non-tasters, a relation between the sensitivity for PTC and the thyroid diseases has been noted^7,8. Recently there seem to have been new developments in the interpretation of this relation⁹.