Aim: This was to study the prevalence of molar incisor hypomineralisation (MIH) among school children residing in a fluorosis endemic area in Tamilnadu (Salem, India). Methods: A target sample of 5000 children of age ranging between 9 and 14 years, comprising 250 children from each of 20 blocks of Salem, participated in this study. The examination was completed in their respective schools by a calibrated examiner using EAPD criteria. Results: Of 4989 children examined, 384 children had MIH, giving a prevalence of 7.3%. The MIH found in girls was 8.9% compared with 6.1% in boys. Single-tooth involvement was seen predominantly in incisors (2.24%), whereas in molars usually three teeth were involved (1.1%). MIH with caries involvement was found in 51% of the teeth. Conclusion: MIH prevalence in this endemic fluorosis district was 7.3%. A gradual increase with age was noted due to post enamel breakdown. Caries involvement was also observed in more than 50% of MIH-affected teeth. © 2015 Elsevier B.V., All rights reserved.