Chronic diseases can arise from modifiable and non-modifiable causes. The study of the causes and circumstances that lead to diseases is called etiology. Using the examples of cardiovascular diseases, chronic joint disorders, viral inflammations, and others, it becomes clear which different circumstances and both endogenous and exogenous factors contribute to the chronicity of a disease. Prevention and the chronic care approach are of great importance in alleviating the suffering of those affected. In chronic diseases with unknown or suspected causes, medical concepts develop only as knowledge increases and are subject to more frequent changes. Good diagnostics, understanding of etiology, (secondary) prevention, and therapeutic intervention can alleviate chronic courses and delay disease progression, but rarely cure. Patient and persistent medical support as part of chronic care is required for all chronic diseases.