The asexual stages of the malaria parasite Plasmodium falciparum develop inside erythrocytes of the human host. Erythrocytes are highly specialized cells lacking organelles and trafficking machinery. The parasite must therefore establish its own transport system to export proteins and waste and import nutrients. A number of parasite-derived structures, implicated in trafficking, appear in the infected red blood cell at the late ring stage. We have identified a novel gene transcribed in ring stage parasites coding for a protein designated the ring exported protein, REX. REX is located in a red cell modification known as the Maurer's clefts, which are parasite induced structures implicated in trafficking of parasite proteins to the red blood cell surface. REX contains predicted coiled-coil regions and a region with similarity to a domain in vesicle-tethering proteins. REX persists in Maurer's clefts throughout the infection of the erythrocyte, where it may play a role in the biogenesis and/or function of this organelle.