So far there is no generally accepted definition of success in the case of dental implants, although criteria differing from country to country have been proposed, which evaluate the success of implants with reference to clinical and X-ray control parameters. The aim of the study was to examine the five most frequently used sets of criteria suggested for determination of the success or otherwise of implants ( Albrektsson, Jahn, Buser, NIH conference, Naert) and ascertain their relative values.In a clinical review, 508 implants (Astra, Frialit-2, IMZ TwinPlus and ITI) were examined and a subjective evaluation of them was made by the patients. Subsequently a statistical analysis was executed (in situ rate, Kaplan-Meier, success criteria).The average observation time of all implants included in the study was 3.5 years, and the in situ survival rate was 95%; Kaplan-Meier survival analysis revealed that the probability of survival after 6 years was 93%. Application of different criteria for success gave very different results (Albrektsson 88%, Naert 89%, NIH 85%, Buser 88%, Jahn and dacute;Hoedt 75%).The increasing importance of quality assurance in medicine makes it necessary to establish standards that will permit reliable comparative analysis of how successful implants are in the future.