TMEM1 (EHOC-1) gene encodes a putative transmembrane protein and is located on human chromosome band 21q22.3. Analysis of a 122,638-bp genomic sequence revealed that TMEM1 gene consists of 23 exons spanning approximately 94 kb and is transcribed in the direction of centromere to telomere. The 5' region of the TMEM1 gene was associated with a CpG island and the 3' end of the TMEM1 gene was mapped just proximal to the 5' end of the neighboring gene PWP2. We determined that the TMEM1 gene encodes a protein of 1,259 amino acids, which is 69-amino acids longer than the previously reported sequence. Since TMEM1 gene is considered to be a candidate for genetic disorders mapped in the 21q22.3 region, the information including complete nucleotide sequence and genomic organization of the TMEM1 gene should be invaluable for the mutation analysis of the corresponding genetic disorders.