Case-only analyses revealed that an interaction existed between cigarette smoking and CYP1B1 1294G allele in CRC (COR = 2.62, 95%CI: 1.01–6.72), the COR for the interaction between CYP1B1 1294G and smoking history > 35 pack-years was 3.47 (95%CI: 1.12–10.80). The gene discussed is CYP1B1; the disease is colorectal carcinoma.