With the development of the European Academy of Paediatric Dentistry (EAPD) judgment criteria, there has been increasing interest worldwide in investigation of the prevalence of demarcated opacities in tooth enamel substance, known as molar-incisor hypomineralisation (MIH). However, the lack of a standardised system for the purpose of recording MIH data in epidemiological surveys has contributed greatly to the wide variations in the reported prevalence between studies. The present publication describes the rationale, development, and content of a scoring method for MIH diagnosis in epidemiological studies as well as clinic- and hospital-based studies. The proposed grading method allows separate classification of demarcated hypomineralisation lesions and other enamel defects identical to MIH. It yields an informative description of the severity of MIH-affected teeth in terms of the stage of visible enamel destruction and the area of tooth surface affected (i.e. lesion clinical status and extent, respectively). In order to preserve the maximum amount of information from a clinical examination consistent with the need to permit direct comparisons between prevalence studies, two forms of the charting are proposed, a short form for simple screening surveys and a long form desirable for prospective, longitudinal observational research where aetiological factors in demarcated lesions are to be investigated in tandem with lesions distribution. Validation of the grading method is required, and its reliability and usefulness need to be tested in different age groups and different populations.