Erythrocyte invasion is a process essential to the survival of malaria parasites. An understanding of the mechanisms that occur during the invasion event is important, since interruption of any of these events would halt the parasite’s asexual cycle and prevent disease. An in vitro erythrocyte invasion was developed by first obtaining parasite-infected cells from mice and purifying them using Percoll gradient centrifugation. These erythrocytes were then cultured with target cells, allowed to mature and release daughter parasites which then invaded the target cells. This assay was then used to study the processes involved in invasion. These assays are simple to use and allow a number of tests to be carried simultaneously. Using this system it was demonstrated that Plasmodium chabaudi chabaudi shows an in vitro preference for immature red blood cells. Whilst RPMI - 1640 is the routinely used medium forthe in vitro cultivation of malaria parasites, we found that it was not the most suitable forthe cultivation of P. c.chabaudi parasites. A number of different media were tested by using each medium as the basal medium in an invasion assay. A combination of B M E and William’s E was found to support the best levels of merozoite invasion and was chosen as the medium of choice for the cultivation of P. c. chabaudi. Target erythrocytes were enzyme treated prior to their addition to invasion assays in order to study the nature of erythrocyte ligands required for parasite invasion. This work led to the proposal that the erythrocyte ligand is a glycoprotein. [35S]methionine-labelled parasites were incubated with murine erythrocytes and a parasite protein of 130 kDa was found to bind specifically to mouse cells. The protein was suggested as a P. c. chabaudi receptor for the recognition of erythrocytes. Polyclonal antibodies were raised against various parasite protein preparations. When these antisera were tested in invasion assays, the levels of invasion were reduced significantly. The specificity of the antibodies was also studied using immunoblotting, immunofluorescence and radio-immunoprecipitation and each antiserum was shown to have a characteristic pattern of reactivity. A monospecific antibody against the 130 kDa putative receptor was also obtained by elution of the antibody from nitrocellulose filters containing parasite proteins to which the polyclonal antisera had been bound.