Implants can be anchored to bone either by a sheath of non-mineralized connective tissue or by osseointegration. The latter gives a firm, intimate and lasting connection. The requirements for osseointegration and the evidence that it occurs are reviewed together with its indications within dentistry. Treatment procedures with jaw-bone anchored bridges on osseointegrated implants are summarized. The series treated comprised about 6000 implants in 1000 jaws of 1000 patients. About 1500 implants were statistically analysed after observation times of 5-12 years. The longest observation period is presently 19 years. Only 14 patients had to revert to removable dentures. The masticatory function of the patients was restored to the same level as that of patients with natural dentitions of corresponding extent. Psycho-socially the patients were almost entirely relieved of their previous severe handicaps related to edentulousness. In all lower and 90 per cent of upper jaws the bridges were continuously stable. The marginal soft tissue reactions were mild and the marginal bone loss less than 1.0 mm during the first year and thereafter only 0.05-0.07 mm annually. After the first year hardly any implants were lost and almost no marginal bone. The implant survival rates were 84 and 93 per cent for those in upper and lower jaws respectively. These results allow a very predictable prognosis to be given for tissue integrated prostheses.