The new forms of drugs with better proprieties from traditional ones were sought for a long time. Erythrocytes applied as carriers of therapeutic substances are among promising. They are characterized by slower release of active substances, less toxicity, as well as better biocompatibility and biodegradation in the organism. It is especially important in administration of drugs with numerous side effects in therapy of chronic diseases e.g. malignancies. Investigations conducted from over twenty years showed, that erythrocytes are universal carriers in which different therapeutic substances were successfully closed, e.g. cytostatics, antibiotics, hormones and vitamins, as well as enzymes and vaccines. Some of the erythrocyte drug delivery systems are now studied at the clinical level, e.g. dexamthasone 21-phosphate in treatment of inflammatory bowel disease and chronic obstructive pulmonary disease. This substance encapsulated in human erythrocytes was also officially registered by European Medicines Agency, as the orphan drug in treatment of cystic fibrosis: Reports on application of carrier erythrocytes in patients with rare genetic diseases have also appeared.