A procedure for measurement of the lingual frenulum in relation to the dimensions of the anterior, inferior segment of the tongue is described and its reliability established. The procedure was validated through physiological studies including speech articulation and oral motor coordination in diadochokinetic movements. Forty subjects were selected from a pool of 210 11–12 year old children and separated into two groups of twenty subjects on the basis of relative length of the lingual frenulum. Significant differences were found between these two groups both in speech articulation errors and in diadochokinetic rates of movement. Findings are discussed with respect to reliability and validity of the procedure. The findings are particularly pertinent to the clinical entity called congenital inferior ankyloglossia or “tongue-tie.”