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We investigated the immunogenicity of recombinant rMSP1 (rPbMSP1) that was generated from Plasmodium berghei. The rPbMSP1 formulated in alum was found to be immunogenic which induced high levels of specific anti-rPbMSP1 antibody. The IgG2a response predominated over IgG1 during the challenge infection in the vaccinated mice. Mice vaccinated with rPbMSP1 in alum mounted significant protective immunity against challenge infection (P<0.01). On day 121 after the booster, three out of ten mice immunized with rPbMSP1 in PBS survived parasite infection (P < 0.05) and eight out of ten mice vaccinated with r MSP1 in alum did (P < 0.01). Hence, immunization with MSP1 in alum obviously has conferred protective effects, which prevented death from P. berghei lethal infection in mice (P < 0.01). These observations provide an excellent model for clinical assessment of this formulation in human subjects. Due to wide spread and increasing resistance of parasites to anti-malaria drugs and the resistance of Anopheles mosquito vectors to insecticides, malaria poses a serious health problem in tropical countries (WHO, 1999). It is estimated that between 300 to 500 million clinical cases and 2.7 million deaths per year are due to malaria. A number of protective antigens have been identified in animal models utilizing several kinds of adjuvants, most of which are toxic and cannot be applied in humans. Further more, the purified antigens tend to lose immunogenicity. Therefore, an effective and safe adjuvant for human use is one of the keys for successful malaria vaccines. Antigen of the invasive blood stage of the parasite, the merozoite has been proposed as a vaccine target (Howard & Pasloske, 1993; Diggs et al., 1993). This molecule has been identified in almost all of the Plasmodium sp. that infect humans, simians and rodents (Holder et al., 1981; Hall et al., 1984). The major constituents of the merozoite surface are polypeptides derived from a high molecular mass precursor protein, merozoite surface protein 1, MSP1. This protein is synthesized during schizogony and its products are localized on the surface of extracellular merozoites. Post-translational proteolytic processing of the precursor molecule generates fragments but only the