In Greece, the need for epidemiological data became evident at the beginning of the mental health reform during 1983 with the emergence of the necessity to develop community-based mental health services. This survey was conducted in 2005 by the Association for Regional Development and Mental Health (EPAPSY), supported by the local authorities. It followed the methodology of the survey "Mental Health in the General Population: Images and Realities" (MHGP), a large scale multisite epidemiological research conducted by the World Health Organization Collaborative Centre of Lille in France and other countries. The aim of this study was to assess prevalence, sociodemographic and comorbidity patterns of mental disorders in the general adult population of Evia Island, Greece. This was a cross-sectional survey investigating point, period and lifetime prevalence of mental disorders. The target population was the non-institutionalized adult population of island of Evia (population 230,000 people). The Mini International Neuropsychiatric Interview and a sociodemographic data questionnaire were administered by trained interviewers to 900 residents of Evia. The quota sampling method was used to obtain a sample representative of the target population. Lifetime prevalence of any disorder, as identified by the MINI, was 29%. The prevalence of depression was high, with 17.5% of women and 14.6% of men currently meeting the criteria for diagnosis. Affective and anxiety disorders were found to be more frequent in women than men, except for dysthymia, social phobia and post-traumatic stress disorder which were slightly more frequent in men. The prevalence of psychiatric disorders in Evia was much higher than the prevalence found by other epidemiological studies in Greece and among the highest in Southern Europe. The high prevalence of mental disorders found in Evia means that almost one third of the population will suffer from a clinically significant disorder in their lifetime. Therefore, the resulting social burden is very relevant and requires the inclusion of mental health care among the main goals of a public health strategy. Methodological issues concerning the comparison of results between different countries, the limitations of the study and the rates of alcohol use disorders discussed. High rates of mental disorders are related to demographic changes, such as the increasing are size of elderly population, and probably to economic hardship and rise in unemployment. Results should be taken into consideration for the planning and development of interventions for vulnerable groups.