The range of mandibular movements was studied on 600 randomly selected people. Mandibular mobility varied widely from subject to subject. There were considerable age and sex differences but no differences were found between the mobility values of persons who were functionally healthy and those with dysfunctions. These factors make it difficult to construct cutoff values that reflect normalcy in mandibular mobility and thus render the clinical utility of such values questionable. The use of age- and sex-corrected border values for mandibular mobility is proposed. The clinical utility of patients' opinions concerning mouth-opening capacity is stressed. On the basis of statistically significant differences, the use of different border values for the protrusive and laterotrusive movements seems to be necessary.