Maturation of Plasmodium falciparum decreases the deformability of infected red blood cells (RBCs), increasing their clearance as they attempt to pass through endothelial slits of the splenic sinus. Previous studies of Plasmodium vivax-infected RBCs led to opposite conclusions with respect to cellular deformability. To resolve this controversy, P. vivax-infected RBCs were passed through a 2-microm microfluidic channel. In contrast to P. falciparum-infected RBCs, mature P. vivax-infected RBCs readily became deformed through 2-microm constrictions. After this extreme deformation, 67% of P. vivax-infected RBCs recovered a normal appearance; however, 15% of uninfected RBCs were destroyed. Results suggest mechanisms for both avoidance of splenic clearance and anemia in vivax malaria.