This report describes a novel mu chain capture ELISA for the detection of IgM antibodies against a Plasmodium falciparum antigen. A fragment of the 220 kDa P. falciparum glutamate rich protein containing amino acid residues 489-1271 was expressed in E. coli as a recombinant chimeric beta-galactosidase fusion protein and used as antigen after purification and biotinylation. Specific IgM antibodies were found in 51% (39/77) of sera from adult Liberians immune to malaria. The binding of IgM antibodies was specific for the malaria portion of the fusion protein and no cross-reactivity was found in sera from patients with IgM antibodies due to other diseases. Inhibition studies with a fusion protein containing amino acid residues 816-1134 (GLURP816-1134) representing the carboxy-terminal repeat region suggested a different use of epitopes for IgM antibodies in different individuals.