The rat glutamate receptor is a 907 amino acid transmembrane protein. Using the rat GluR1 cDNA as a probe, we have isolated cDNA clones from a human hippocampal cDNA library. Sequence of a full length cDNA clone revealed 98.2% and 89.4% identity to the rat sequence at the amino acid and nucleotide levels respectively. The human cDNA clone detected an RNA transcript in human cerebral cortex, hippocampus and cerebellum, similar to that seen in rat. In situ hybridization experiments showed that human GluR1 mRNA is present in granule and pyramidal cells in the hippocampal formation and that there is no apparent difference of distribution between control patient and patient with Alzheimer's disease. Dot blot analysis of flow-sorted human chromosomes showed that the GluR1 gene maps to chromosome 5.