MIH was defined by Weerheijm (2001) as hypomineralisation of systemic origin of 1-4 permanent first molars, frequently associated with affected incisors. The diagnostic criteria include the presence of demarcated opacity, posteruptive enamel breakdown, atypical restoration, extracted molar due to MIH and unerupted teeth. The etiologies are divided into five groups: Exposure to environmental contaminants, pre/peri and Neonatal problems, exposure to fluoride, common childhood illnesses and medically compromised children. The prevalence of MIH varies between 2.8% and 25%, dependent upon the study. The clinical implications include highly sensitive teeth, difficulty to achieve adequate anesthesia, behavioral problems and anxiety, rapid progression of caries and esthetic implications. A six step approach to management is suggested: risk identification, early diagnosis, remineralisation and desensitisation, prevention of caries and posteruption breakdown, restorations and extractions and maintenance. The key for a successful treatment is early diagnosis, intense follow up and usage of remineralisating agents as soon as the teeth erupt. This case report demonstrates a treatment plan in a 8.5 years old boy who has MIH, which includes the diagnosis, treatments, and follow up for 21 months.