Traditional medicine has been using earthworms to treat a wide range of pathological conditions for many centuries. Current research focuses primarily on the isolation and characterization of biologically active compounds, including notable examples such as glycoprotein G90, which exhibits thrombolytic and antitumor properties; the enzyme complex lumbrokinase; and the extracellular oxygen transport protein erythrocruorin, regarded as a potential basis for blood substitute development. Model organisms such as Caenorhabditis elegans, which are used to study the mechanisms of aging, neurodegenerative diseases, and evaluate the effectiveness of medicines, also play an important role. Bioluminescent systems of annelids are of particular interest because they exhibit a variety of chemical mechanisms of luminescence and unique cofactors that hold promise for applications in biomedicine. The combination of these properties and abilities underscores the importance of worms as a source of enzymes, proteins, and metabolites, as well as model systems for finding solutions to both fundamental and applied biomedical problems.