In principle, only patients with an ASA (American Society of Anaesthesiologists)-score I or II qualify for an elective surgical procedure, such as an implantation treatment. Surgical risks are weighed against the potential benefits offered by oral implants. Counter-indications to implant rehabilitation include recent myocardial infarction and cerebrovascular accident, immunosuppression, active treatment of malignancy, drug abuse, as well as long-standing intravenous bisphosphonate use. In the case of patients with an endocarditis risk, and also in the case of patients with an orthopedic prosthesis, implants should be placed with some reluctance. If the decision is made for treatment, then consultation with the treating specialist is recommended. Beside absolute counter-indications, there are also conditions which compromise the success of an implant treatment, such as radiation of the jaw or long-term smoking. Concerning the effect which medical conditions have on the life-expectancy of the implant, little is known. There appear to be few existing factors which actually have a negative influence on the chance that an implant will survive.