In this application is the expression and purification of a recombinant Plasmodium falciparum (3D7) MSP-1.sub.42. The method of the present invention produces a highly purified protein which retains folding and disulfide bridging of the native molecule. The recombinant MSP-1.sub.42 is useful as a diagnostic reagent, for use in antibody production, and as a vaccine.