Genotyping of TYMS (5′TRP and 3′UTR), UGT1A1*28, UGT1A9*22 and UGT1A7*3 was performed in 149 metastatic CRC patients treated with irinotecan/5FU as first-line chemotherapy enrolled in a randomised phase 3 study. This evidence concerns the gene UGT1A9 and colorectal carcinoma.