Many of the presently used methods of evaluating osseointegration at second-stage surgery are highly subjective. The Periotest is claimed to offer a more objective means to assess osseointegration by means of microcomputer-controlled percussion. In 1991 the Dental Implant Clinical Research Group initiated a long-term clinical study in cooperation with the Department of Veterans Affairs to investigate the influence of implant design, application, and site of placement on clinical performance and crestal bone height. As part of this investigation, the Periotest values for 1,565 root form implants were determined at second-stage surgery and correlated with type, material, coating, diameter, and length. Hydroxyapatite-coated implants and increased implant diameter and length produced Periotest values that indicated a greater extent of stability as compared with noncoated implants with shorter diameters and lengths. Hydroxyapatite-coated cylinder-type implants yielded the most favorable Periotest readings. Not only does the Periotest have the potential of being a valuable instrument for assessing implant mobility at second-stage surgery, but it also appears to have the capability of determining slight differences in the implant-bone complex.