The aim of this study was to investigate the proportion of 3 Neil's classifications of lateral throat forms and the difference in the length of the lateral throat form between the dentures and the patient's actual anatomy. The classification of lateral throat form was determined by the patient's functional movements, and an implant depth gauge was used to measure the length of the lateral throat form in the patient's mouth and compare it to that of the dentures. One hundred mandibular edentulous patients were measured. The proportion of Neil's Class I lateral throat form was 70%, the proportion of Class II was 25%, and the proportion of Class III was 5%. The mean difference between the actual lateral throat forms and the dentures was 6.7 ± 2.9 mm at the anterior point of measurement (from the anterior part of the retromolar pad to the mouth floor) and 10.0 ± 3.7 mm at the posterior point (from the middle of the retromolar pad to the mouth floor). The difference in length between the ridge height of the mouth and the denture was statistically significant (P .001).