Several cDNA clones encoding the human glutamate receptor subunit GluR3 flip and flop isoforms, were isolated from human hippocampus and fetal brain libraries. DNA sequence analysis revealed overlapping clones permitting the reconstruction of full-length GluR3-flip and GluR3-flop cDNAs. The GluR3 cDNAs demonstrated an 94.1-94.7% nucleotide (nt) identity with the corresponding rat cDNAs. The nt sequence of the GluR3 cDNAs would encode 894 amino acid proteins that have a 99.4% identity with the rat GluR3 isoforms. The human GluR3 cDNAs predict an additional 6 amino acid in the N-terminal signal peptide as compared to the rat GluR3.