Objective:To select the optimal internal reference genes for gene expression analysis in colorectal tumor tissues. Methods:The total RNA of colorectal cancer tissues from 10 patients weve studied. The mRNA transcription profiles of five frequently used housekeeping genes,including GAPDH,ACTINB,UBC,HRPT1,and 18S rRNA,were tested by real-time quantitative RT-PCR. The stability of these control genes was analyzed by geNorm and NormFinder softwares. Results:The M value of GAPDH and ACTINB was the least and identified as the suitable and stable internal reference gene combinations using geNorm software. The M volue of 18S rRNA was the highest and its stability was the lowest. Furthermore,GAPDH was the most stable reference gene,which was followed by UBC using NormFinder software. Conclusion:The combination of GAPDH and ACTINB,but not 18S rRNA and HRPT1,is the most reliable reference gene group for normalization of real-time RT-PCR in colorectal tumor tissues.