Objectives: To evaluate and compare the buccolingual inclinations of maxillary and mandibular first molars in untreated children and adults. Materials and Methods: One hundred and thirty-eight subjects were selected and divided into three groups, as follows: (1) age 6-9 years, N ¼ 46; (2) age 10-19 years, N ¼ 56; and (3) age 25-35 years, N ¼ 36. For each subject, existing cone beam computed tomography images were used, and the long axis for each maxillary and mandibular first molar was determined. The converge angles formed by the long axis of left and right maxillary first molars and by the long axis of left and right mandibular first molars were measured. Results: The maxillary molars exhibited buccal inclination, with the converge angle of 21.18 6 9.58 in group 1, 17.38 6 8.68 in group 2, and 9.38 6 7.38 in group 3. Statistically significant differences were found between groups 1 and 3 and groups 2 and 3, but not between groups 1 and 2. The mandibular molars exhibited lingual inclination, with the converge angle of 34.98 6 118 for group 1, 26.68 6 9.28 for group 2, and 26.18 6 7.78 for group 3. Statistically significant differences were found between groups 1 and 2 and groups 1 and 3, but not between groups 2 and 3. Conclusions: Maxillary first molars exhibited buccal inclination. Adults displayed less inclination than did children. Mandibular first molars exhibited lingual inclination. Adults displayed less inclination than did children. Some degree of curve of Wilson should be maintained at the end of orthodontic treatment to fulfill physiologic needs and stability. (Angle Orthod. 2019;89:87-92.)