A CONTINUING controversial issue in medical audiology during 1964 was the recommendation to change the "zero" audiometer reference level. The proponents of this change pointed out that the new standards proposed by the International Standards Organization would put an end to confusion and ambiguity and make for a uniform standard throughout the world. They also cited numerous disadvantages of the old standard that they felt would be overcome by the proposed standard. The opponents agreed in principle that a new standard was advisable but were firmly convinced that the proposed ISO changes did not supply the answer. They felt that a new standard should be based on physical measurements, such as acoustical "0," and not on a biological determination that may require further change in the future when more sophisticated testing techniques are developed. The chief opposition to the ISO standard came from industrial groups who were concerned about the