The expression “genetic disease” suggests the idea that one or more genes cause a disease. Since the identification of the so-called disease-causing genes, many genetic variants associated with common diseases such as diabetes or cancer have been identified. But if the involvement of genetic factors in the development of a condition justifies labeling it “genetic,” the definition of genetic disease is likely to become trivial. Indeed, all human diseases would be genetic, since virtually every medical condition, disease susceptibility, or response to treatment is caused, regulated, or influenced by genes. Moreover, genes alone are not responsible for the development of diseases: their etiology is complex with many factors interacting with each other. So when is giving primary importance to genetic factors justified? The history of medicine may help us see which biological and technological advances have influenced conceptualization of genetic disease, while philosophical analyses of the causal selection problem may help us better understand how one might justify claims that genes are the main causes of certain diseases. The last part of the article examines interactionist attempts to deal with genetic factors involved in human diseases and particularly network medicine.