The place of orthorexia nervosa (ON)--described by Bratman in 1997--is not clearly defined in the diagnostic systems. However, the increasing number of clinical experiences and research data gives us more and more information about the epidemiology, and the social and individual characteristics of ON. The general population shows a 6.9% prevalence of ON; healthcare professionals are at high risk of ON with the prevalence rate of 35-57.6%. Education, the choice of profession, socioeconomic status and the internalization of the ideals of society are significant factors in the development of ON, while sex, age and body mass index do not seem to be determining variables in this respect. The lack of common criteria and proper research results on ON makes it impossible to generalize data on the general population. Further studies with larger representative samples and assessment instruments with good psychometric properties are necessary to make research data on ON comparable.