A total of 68 patients, 26 men and 42 women, aged 21 to 86 years, were treated with 204 endosseous implants (TPS, ITI, Bonefit, or Biolox) from 1985 to 1990. They were examined at their latest recall visit approximately 22.5 months after surgery, the range varying greatly between the implant systems used (from 4 to 60 months). Fourteen implants were lost during the observation period because of failures in osseointegration. There were no statistically significant differences in success rates between the implant systems during the observation period. The Periotest values, however, differed between the Bonefit and ITI implants in maxillae (P .001) and mandibles (P .01), and between successful and failed TPS implants (P .001, unpaired t test). In four of the failures, all ITI implants, the prosthetic restorations (fixed dentures and single crowns) had been lost. All other failures were treated by using the previous complete denture. Possible causes of failure included advanced age and poor general health of the patient, complications in the surgical procedures, and compromised oral hygiene. Schlagwörter: complications, oral implants, Periotest