Treatments summarized under the term "natural medicine," i.e., those offered as an alternative or in addition to conventional medicine, have enjoyed a surge in popularity in recent years. The "natural" descriptor employed in connection with these healing methods is frequently misunderstood, leading to underestimation of the risks arising from incorrect use. However, the essential principle underlying traditional natural medicine, mobilization of the body's own forces against disease, is increasingly being employed in a new, rational form of medicine: molecular medicine. A range of natural endogenous substances for medical use are already available. Human proteins such as erythropoietin can now be produced as medicines in highly pure form with the aid of genetic engineering techniques. Our increasing understanding of the function of our genes and the resulting descriptions of molecular mechanisms underlying disease are also helping us to utilize the body's own construction set. New techniques such as gene therapy will in future enable us to reproduce the natural conditions in the healthy body with increasing specificity in our attempts to cure illnesses. One such application will be the activation of the immune system to combat cancer. The complete decoding of the human genome will not only allow illnesses to be described, and possibly prevented, at an earlier stage. Illnesses will also be able to described more precisely and individually at the molecular level, opening up the possibility of targeted, patient-specific cures.