The authors studied a population of 4.023 subjects from several rural and urban communities selected on the basis of age, work tasks and social class. Genetic predisposition to essential hypertension was evaluated by determining intraerythrocyte sodium levels in all subjects with essential hypertension and their families. The authors also verified the behaviour of some biohumoral factors (PRA, aldosterone, ANP, intraerythrocyte, Na) as possible markers of essential hypertension and the role of some acquired risk factors in the development of the disease and its cerebrocardiovascular complications. The hypertense subjects were divided into groups and treated with diet alone or diet associated with drugs depending on the prevalence of pathogenetic factors. The results were evaluated after 1, 3, 6 and 12 months.