Objective Differential expression analysis and cloning of murine thymic aged-related genes. Methods Different expressions of thymic mRNAs from 1- and 10-month old mice were analyzed via DDRT-PCR and different expression sequence tags (ESTs) were obtained, following by identification with Northern Blotting, DNA sequencing, as well as screening of cDNA library. Results It was found that there would be a significant difference of gene expression in murine thymuses. Gene expression of some genes were exclusive in thymus from 1 or 10-month old mice, while some expressed different with age.108 differential display cDNA fragments were recovered, among which 31 were positive for hybridization by Northern blot. After sequenced, 14 ESTs were found to share high homology to known genes, whereas remaining 17 were novel. A murine thymic cDNA library was screened by using one cDNA fragment that expressed with higher level in total RNA of l-month old murine thymic tissues than 10-montholds. Finally, one 1470 bp fragment was cloned and showed a 99% of homology to murine transketolase.Conclusion Expression of murine thymic genes has displayed a marked difference with age. These genes might be participated in thymic atrophy.