Objectives: The aims of this study were to: (1) determine the frequencies of Carabelli trait on upper first permanent molars
(2) compare the Carabelli trait between the Viet and Katu, Ede, Cdho ethnics. Materials and method: With the descriptive study design on a longitudinal follow, the sample consisted 64 pairs of dental casts (32 boys, 32 girls, from 12 to 14 years-old). Carabelli trait were evaluated, classified according to Dahlberg method (1956). Results: The frequency of pit, groove form was highest (39.06 percent). In contrast, the frequency of tubercular form was lowest (25 percent). There was no significant difference of Carabelli trait between the Viet and Katu, Ede, Cdho ethnics (p 0.05). Conclusions: The frequencies of tubercular form of Carabelli were lowest in the Viet and Katu, Ede, Cdho dentition. There was no significant difference of Carabelli trait between the Viet and Katu, Ede, Coho ethnics (p 0.05).