We have isolated a human cDNA that is highly homologous to the murine gene (Gpm6) encoding a membrane glycoprotein, M6. The human gene (GPM6A) contains an open reading frame of 834 nucleotides encoding a peptide of 278 amino acids. Northern-blot analysis revealed specific expression in human brain. We assigned the GPM6A locus to chromosome bands 4q33-->q34 by radiation hybrid mapping.