Introduction: Constanta county is a Romanian region characterized by a high endemicity (6 cases/100.000 inhabitants) of hydatidosis. This represents a public health problem due to medical and social implications. Specific traditional way of life in Constanta: high number of domestic animals (sheep, cows, goats) are complicated by new epidemiological issues, such as high number of stray dogs, lack of anthelmintics prophylaxis and recommended vaccination in well- cared and stray dogs, specifically presence of dogs on the beach, contaminating the sand. In this article we describe the epidemiological data obtained during a more complex study. The results of the study were presented at the 17th European Congress of Clinical Microbiology and Infectious Diseases (ECCMID) and 25th International Congress of Chemotherapy (ICC) in April 2007. Objectives. Evaluation of the interdependence between the links of the epidemic process (source of infection, route of transmission and vulnerable population) and various environmental factors that directly or indirectly contribute to the complex epidemiology of this disease. Material and method. We perform a prospective study on 320 patients diagnosed with hydatid cysts between 2001 -2006 from different places in Constanta county. Studied patients were ask to respond to a questionnaire regarding epidemiological aspects of hydatidosis. Results. The patients distribution per sex showed a higher incidence of this disease in women, compared to men; however, there is no significant relationship between hydatidosis and the risk of emergence in women. It is noticed that the highest number of studied cases is the age group 50-59 years old, that was contaminated at the active age, around 40 years old. The case distribution based on the social environment highlighted: a high number of cases from the urban area (234 cases, 72%), especially in Constanta city (182 cases), compared to the rural area (88, 28%). The greatest number of patients belong to the Romanian ethnic group and they represent the majority in our city and county. The second group are the Macedo-Romanians who represent a significant group in Constanta county and are well-known animal breeders, especially sheep. The epidemiologic inquiry was positive in most of the cases, the most of the patients admitted the contact with domestic animals (sheep, cattle, goats and dogs). Out of the 320 patients, 71 had already diagnosed with hydatid cyst in the past. It is noticed that the number of cases diagnosed with hydatidosis in our clinic significantly increased in the last years. Conclusions. The numerous sources of infection (dogs) and intermediary hosts (herbivorous) living in Dobrogea area maintain the disease endemicity. Given the minimization of the direct transmission through the improvement of the individual hygiene, the indirect transmission route is preponderant through contamination of the environment and a collective faulty hygiene.read more..