Purpose of ReviewHuman erythrocytes are responsible for oxygen delivery in the body. Erythrocytes are a product of terminal differentiated erythroid cells that accumulate hemoglobin and exclude nuclei. The long-held conventional wisdom has been that mature erythrocytes lack any genetic materials. Contrary to this view, accumulating evidence from multiple groups indicates that erythrocytes contain abundant and diverse RNA species. These newly discovered genetic materials suddenly open up opportunities to re-examine many diseases affecting erythrocytes.