The purpose of this report is to alert the foodservice industry, particularly the fast-food industry, of an emerging health issue. Considerable evidence has accumulated over the past two decades that heated cooking oils, especially polyunsaturated oils, may pose several types of health risks to consumers of fried foods and even people working near deep fat fryers. Heat degrades polyunsaturated fatty acids to toxic compounds; saturated and monounsaturated fatty acids are resistant to heat-induced degradation. Several types of diseases may be related to the exposure of humans to food- or air-borne breakdown products of heated oils including atherosclerosis, the forerunner to cardiovascular disease; inflammatory joint disease, including rheumatoid arthritis; pathogenic conditions of the digestive tract; mutagenicity and genotoxicity, properties that often signal carcinogenesis; and teratogenicity, the property of chemicals that leads to the development of birth defects. Factors that can contribute to improved oil stability, and therefore fewer health concerns, are briefly discussed. The literature reviewed raises serious questions concerning the willful addition of large amounts of polyunsaturated fatty acids into the human diet without accompanying measures to ensure the protection of these fatty acids against heat- and oxidative-degradation. It is hoped that this review will stimulate interest in the foodservice industry in this important area of potential health concern, and also foster the research and development activities necessary to reduce the exposure of humans to lipid oxidation products.