Abstract: In order to clarify the relationship between the polymorphism of N-Acetyltransferase (NAT) and genetic susceptibility to gastrointestinal Carcinoma. Phenotypy of NAT polymorphism was determined among 70 patients with gastrointestinal carcinoma (34 gastric cancer. 28 colerectal cancer and 8 primary liver cancer) and 107 health controls in Fujian. The results showed that the slow type of NAT was 38 57% (27/70) for cases, and 18 69% (20/107) for the controls. The difference between the cases and controls was statistically significant ( x²=8 15, P =0 0043).The odds ratio was 2 67 (95% CI 1 28～5 61), which suggest that persons with slow type NAT have 1 67 times of the increased risk of gastrointestinal carcinoma, This investigation would throw a new clue into the study of aetiology and prevention of gastrointesinal carcinoma.