The present invention relates to method and kit for performing a colorectal cancer assay. Especially a method including extracting total RNA from a peripheral blood sample obtained from a patient suspected of having or having colorectal cancer; contacting the total RNA, or cDNA or cRNA obtained from the total RNA, with one or more reagents specific for at least one target gene and no more than 100 target genes; and measuring the expression level of the at least one target gene and no more than 100 target genes. The at least one target gene and no more than 100 target genes includes one or more members selected from the group consisting of the KLRB1, KLRC2, KLRC3, KLRD1, KLRK1, CD247, RRAS2, SH2D1B, LCK, MRPS6, SPRY4, CYBB, DUSP2, PDE4D, SH2D2A, GZMB, INSR, ITGAM, VCAN, CD163, P2RY10, CD226, MRPL10, ITPRIPL2, CD2, and NUDT16 genes.