AbstractPreviously published results of short-term tests (STT) applied to chemicals, identified as carcinogens and noncarcinogens, are compared and discussed. Inspection of the data shows that carcinogens and noncarcinogens are about equally STT-positive. Although it may be possible to observe suggestive indications in the data, it is difficult to be certain that these indications are necessarily relevant to or predictive of human carcinogenic risk. The assumption that STT are predictive, if incorrect and accepted, would seem to have the potential for causing harm to public health by leading to falsely recognized carcinogens as noncarcinogens and noncarcinogens as carcinogens. Technological and legal preparations have been made for rapid regulatory decisions on the basis of STT. The data, however, appear to caution against utilizating these means too quickly.