In the past 50 years the driving force in medicine has been the development of drugs and procedures to modify the pathophysiology of illness. As viewed from the trenches of medical practice, the advances in drug therapy, although notable and clearly helpful, appear to have reached a plateau. Most of the "new" drugs over the past several years are primarily variants of old drugs. By comparison, the impressive advances made by basic scientists, biochemists, and molecular biologists, are only now beginning to be appreciated by the medical profession, and the enormous potential of these basic science advances has yet to be pursued. Modern medicine seems to be based on an "attack strategy", a philosophy of treatment formed in response to the discovery of antibiotics and the development of surgical/anesthetic techniques. Disease is viewed as something that can be attacked selectively - with antibiotics, chemotherapy, or surgery - assuming no harm to the host. Even chronic illnesses, such as diabetes and hypertension, yield simple numbers which can be furiously assaulted with medications. Amidst the miracles and drama of 20th century medicine we may have forgotten the importance of host support, as if time borrowed with medications and surgery were restorative in and of itself. Yet, in this age, a patient may be cured of leukemia through multiple courses of chemotherapy and bone marrow transplantation, only to die slowly of unrecognized thiamine (vitamin B1) deficiency(47). Like the vitamins discovered in the early part of this century, CoQ10 is an essential element of food that can now be used medicinally to support the sick host in conditions where nutritional depletion and cellular dysfunction occur. Surely, the combination of disease attacking strategy and host supportive treatments would yield much better results in clinical medicine. Since CoQ10 is essential to the optimal function of all cell types, it is not surprising to find a seemingly diverse number of disease states which respond favorably to CoQ10 supplementation. All metabolically active tissues are highly sensitive to a deficiency of CoQ10. CoQ10's function as a free radical scavenger only adds to the protean manifestations of CoQ10 deficiency. Preliminary observations in a wide variety of disease states have already been published (48,49,50,51,52,53,54,55,56,57,58). One of the disease states which has received attention is cancer. Low levels of CoQ10 in the blood of some cancer patients have been noted (59), but overall, there is little data regarding cancer. The best work to date documents a significant reduction in the cardiac toxicity of the chemotherapy drug, Adriamycin (52,53,54). The cardiac toxicity of Adriamycin and related drugs may well relate to free radical generation and this might explain the benefit of CoQ10 in its capacity as a free radical scavenger. The studies on Adriamycin cardiotoxicity were of short duration and did not specifically note any favorable or detrimental effect on the clinical course of the cancer itself. It is reasonable to assume that optimal nutrition (which would include optimal levels of CoQ10) is generally beneficial in any disease state, including cancer. Another interesting topic is the relationship between the immune system and CoQ10. Immune function is extraordinarily complex and undoubtedly is influenced by numerous nutritional variables. There are some encouraging preliminary data from the study of AIDS patients(50,51). End stage AIDS, like other overwhelming illnesses, has been associated with a significant deficiency in CoQ10. Regarding AIDS and cancer, it would be foolish to make premature statements about future utility of CoQ10, but it is even more foolish to ignore the importance of adequate CoQ10 levels in these disease states. Adequate CoQ10 supplementation (with close attention to plasma CoQ10 levels) is analogous to adequate hydration, and any treatment of critically ill patients should not ignore this easily measured and correctable deficiency. The antioxidant or free radical quenching properties of CoQ10 serve to greatly reduce oxidative damage to tissues as well as significantly inhibit the oxidation of LDL cholesterol (much more efficiently than vitamin E) (60,61). This has great implications in the treatment of ischemia and reperfusion injury as well as the potential for slowing the development of atherosclerosis. In keeping with the free radical theory of aging, these antioxidant properties of CoQ10 have clear implications in the slowing of aging and age related degenerative diseases. There is epidemiologic evidence in humans that uniformly shows a gradual decline in CoQ10 levels after the age of twenty. Until recently, attention has been focused on requirements for CoQ10 in energy conversion in the mitochondrial compartment of cells or on the antioxidant properties of CoQ10. New evidence shows that CoQ10 is present in other cell membranes. In the outer membrane it may contribute to the control of cell growth, especially in lymphocytes (the implications are far reaching(62,63,64,65)). The clinical experience with CoQ10 in heart failure is nothing short of dramatic, and it is reasonable to believe that the entire field of medicine should be re-evaluated in light of this growing knowledge. We have only scratched the surface of the biomedical and clinical applications of CoQ10 and the associated fields of bioenergetics and free radical chemistry.