The development of endosseous implants has proven to be one of the most significant benefits dentistry has offered its patients to restore predictable oral function and improve their quality of life. There do exist however, some whose medical condition or medications preclude the successful placement and retention of fixtures. Over the years the number of these compromising situations has decreased, and will continue to do so, as a better understanding of metabolic and pathologic processes is forthcoming, as well as a willingness by dentists and physicians to explore those perceived contraindications that may not be justified. This manuscript reviews conditions previously thought to be, and those that actually are not, indications for implant placement as a guide for the practicing implantologist. It is present history only and by no means implies that subtractions and additions may not be forthcoming.