A gene encoding a 352 amino acid protein with a putative signal sequence, transmembrane domain and thrombospondin structural homology repeat was identified in the genome of the human malaria parasite, Plasmodium falciparum and the rodent malaria parasite, Plasmodium berghei. The protein localises in the apical organelles of P. falciparum and P. berghei merozoites within intraerythrocytic schizonts and has, therefore, been termed the Plasmodium thrombospondin-related apical merozoite protein (PTRAMP). PTRAMP co-localises with the Apical Merozoite Antigen-1 (AMA-1) in developing micronemes and subsequently relocates onto the merozoite surface. Although the gene appears to be specific to the Plasmodium genus, orthologues are present in the genomes of all malaria parasite species examined suggesting a conserved function in host-cell invasion. PTRAMP, therefore, has all the features to merit further evaluation as a malaria vaccine candidate.