THE REACTION OF THE PERIODONTIUM to a defined percussive force applied in an orofacial direction can be evaluated by a mobility meter. The elastic and viscous characteristics of the periodontium ate evaluated by the device from the contact time between tapping head and the tooth, and reported as a numeric value called the PTV. In this study, the relation between PTVs and bone loss (BL), clinical attachment level (CAL), probing depth, bleeding on probing, and plaque and gingival indices were evaluated in 35 patients with moderate to advanced periodontal disease. The effects of gender, smoking, and initial periodontal therapy on PTVs were also evaluated. Repeated measures analysis of variance was used to determine whether the relationship between PTVs with CAL and BL was dependent on tooth type. Stepwise multiple linear regression was used to test which of the clinical parameters and bone loss would produce the highest predictive value with PTVs. The effects of gender and smoking on PTVs were examined by analysis of covariance. The changes in clinical parameters and PTVs before and after treatment were evaluated by repeated analysis of variance. PTVs were found to give the highest predictive value with bone loss. However, the correlation was observed to be dependent on the location of the tooth in the jaw and the tooth type. Interproximal and midpoint clinical attachment level measurements showed that PTVs correlated more strongly with the overall support, rather than the support on the direction of the percussive movement. No pronounced differences of PTVs were noted between gender. PTVs of smokers were observed to be higher than non-smokers. There was no significant change of PTVs after the initial phase of periodontal therapy. This cross-sectional study shows that the mobility meter evaluation was primarily related to the amount of bone loss while being significantly affected by the location of the tooth in the jaw. Factors such as severity of gingival and sulcular inflammation, oral hygiene, and gender do not seem to have an effect on PTVs.