The putative protein C7orf24 is encoded by Homo sapiens chromosome 7 open reading frame 24. C7orf24 was first identified as a 21-kDa cytochrome c-releasing factor detected in the cytosolic fraction of human leukemia U937 cells after treatment with geranylgeraniol. C7orf24 protein was recently identified as a gamma-glutamyl cyclotransferase, an enzyme in the gamma-glutamyl cycle. However, the exact localization of C7orf24 mRNA in normal tissues remains unknown. The present study examined the distribution pattern of C7orf24 mRNA in rat tissues using reverse transcription-polymerase chain reaction (RT-PCR) and in situ hybridization histochemistry. The RT-PCR experiments demonstrated that C7orf24 and a variant C7orf24 mRNA were expressed in various tissues. Quantitative RT-PCR analysis revealed significantly high levels of both C7orf24 mRNAs in the liver and kidney, compared with other tissues examined. In situ hybridization histochemistry localized C7orf24 mRNA to hepatocytes in the liver and renal tubules in the kidney. The present results thus implicated an important role for C7orf24 in liver and kidney.