The number of human cases with hydatidosis in the Province de Río Negro in the period 1969-1983 was determined by a retrospective exam of the registers at the Provincial Ministry of Health. From 1216 cases the yearly numbers between 59.4 in 1969-78 and 124.4 cases between 1979-83. This implies a yearly of 3.24 X 10,000 and with the most frequent localization in the liver. The average days of hospitalization was 29.2 per patient. The highest correspond to the southern departments of the Province 6.57 X 10,000 in the 40 Sanitary Zone. Eighty two and thirty five per cent of the cases had immunological confirmation with DD5, before surgery. The census allowed us to determine that rates of prevalence were in school children 1.09%, in conscripts, 0.28% and in adult settlers 2.58%. The average of positive serological cases in the province, was 0.77%. The yearly number of cases diagnoses is estimated in 4% of the existent carriers and is the highest in the world. The followup and control of children who had surgery, allowed us to detect that 30% of the cases presented new hydatid cyst before the 5 year lapse. Different factors put Río Negro with the highest rates of denounced human hydatidosis. These are related to living conditions around cattle farms and the socio economics and educational factors, which are analyzed in this paper. Modifications in the Programme for the control of hydatidosis has been put into action by the sanitary authorities.