Progress in molecular biology and genetics is changing the practice of medicine and public health through the development of molecular diagnostics and targeted interventions for susceptible individuals. The ethical, legal and social issues that are becoming apparent as these important discoveries are introduced into practice will have an enormous impact on society. The accurate translation of this new genetic information from the laboratory to the community is an urgent need. Molecular epidemiology is at the foundation of this important link, and represents the scientific basis of public health for the 21st Century. (Rev Méd Chile 2000; 128: 1261-68)