Application of erythrocytes, the most abundant cells of the human body with desirable physiologic and morphologic characteristics, in drug delivery has been exploited extensively. These cellular carriers, having remarkable biocompatibility, biodegradability, and life-span in circulation, can be loaded by a wide spectrum of compounds of therapeutic value using different chemically, as well as physically, based methods. Most of the characteristics of the erythrocytes, including shape, membrane fragility, deformability, and hematologic indices undergo some degree of irreversible changes during the loading procedure. The efflux pattern of the encapsulated compounds from the carrier erythrocytes covers a wide range between a relatively rapid release (complete release within a few hours) and no detectable release until the cell lysis. A series of methods have been tested successfully for improvement of in vitro storability of the carrier erythrocytes without any significant changes in cell biology as well as drug delivery efficacy. Carrier erythrocytes have been exploited for several potential applications, including intravenous slow release of therapeutic agents, enzyme therapy, drug targeting to reticuloendothelial system (RES), improvement of oxygen delivery to tissues, and preparation of fused cells.