We have characterized a glutamate rich Plasmodium falciparum antigen, GLURP, which by immunoassays appears to be present in both the pre-erythrocytic and erythrocytic stages of the vertebrate life cycle. The gene, which is located on chromosome 10, encodes a polypeptide of 1271 residues with a predicted molecular mass of 145 kDa. Rabbit antiserum against a fusion protein expressing the C-terminal end of the molecule detects a protein with a molecular mass of 220 kDa. The sequence includes two hydrophobic regions: one consisting of 23 residues and located by the N-terminus which may act as signal peptide, and the second located at the C-terminus consisting of 33 predominantly hydrophobic residues. Except for these hydrophobic regions the protein is hydrophilic and highly charged. The sequence has two tandem repeats designated as R1 and R2. These regions were found to be conserved in isolates from different geographical areas. High levels of anti-GLURP antibodies have been shown to correlate with low parasite density. The indication of GLURP being present in all stages of the parasite in the human host raises significantly the prospects of the potential of this molecule.