We investigated the quantitative expression of the human glucose-6-phosphate translocase gene (G6PT1) and its splicing variants in human tissues. The G6PT1 gene was strongly expressed in liver, kidney and haematopoietic progenitor cells, which might explain major clinical symptoms such as hepatomegaly, nephromegaly and neutropenia in glycogen storage diseases type Ib. Reverse transcriptase-mediated PCR amplification of G6PT1 cDNA revealed several splicing variants in tissue-specific manners. The brain-specific isoform, which has an additional 22 amino acids between exons 6 and 8, was also identified in heart and skeletal muscle. A new splicing variant, although less prominent in quantity and lacking polypeptide loops corresponding to exons 2 and 3, may have a distinct substrate affinity or specificity in leukocytes and haematopoietic progenitors. In conclusion, the G6PT1 gene was expressed in various tissues, and alternative splicing variants exist in tissue-specific manners.