Lingual orthodontics is used clinically. This study investigated the lingual crown angulation and inclination of optimal occlusion in Taiwanese people. The sample included 45 sets of dental study casts from 28 males and 17 females with optimal occlusion selected from approximately 5,000 young adults. Mesial tipping occurred in all teeth except the upper second molars, the lower central incisors, and the lower lateral incisors. The greatest mesial tipping was observed in the lower second molars. The greatest distal tipping was observed in the lower lateral incisors. Labial (buccal) inclination was observed in all teeth except the lower first molars and the lower second molars. Maximum labial inclination occurred in the upper central incisors. Maximum lingual inclination was observed in the lower first molars.