4641 Background: There has been an increase in the diagnosed incidence of LGNET in US over the last 2 decades. Little is known about the etiology of LGNET. In this hospital-based, case-control study we evaluated the association of cigarette smoking, alcohol consumption, diabetes mellitus (DM) and family history of cancers with LGNET of different sites. Method: Cases were patients with LGNET referred to The University of Texas M.D. Anderson Cancer Center between 12/1999 and 9/2005. Controls were selected from healthy individuals who accompanied patients with other cancers. Logistic regression was applied to estimate the adjusted odds ratio (AOR) and 95% confidence interval (CI) for potential risk factors and demographic characteristics. Result: We identified 951 LGNET patients with primary sites including appendix (n=102, 10.7%), small bowel (n=234, 24.6%), lung (n=149, 15.7%), pancreas (n=166, 17.5%), stomach (n=55, 5.8%), rectum (n=56, 5.9%), and others (n=189, 19.2%). Cases were compared to 924 controls. Majority of subjects were white-race (cases, 79.7%; controls, 89.5%). Gender distribution was similar in LGNET patients with 1:1 ratio. DM was associated with pancreatic and gastric primary sites; AOR and 95% CI were 2.5 (1.6–3.9) and 4.5 (2.2–9.3) respectively. Ever cigarette smoking was associated with lung carcinoid (OR=1.3; 95%CI, 1.01–1.9) especially among heavy smokers (20 cigarettes per day), (OR=1.7; 95%CI, 1.01–2.9). Ever or heavy alcohol consumption (= 60 ml ethanol/day) was not significantly related to LGNET of any site. The significantly elevated risk for carcinoid tumors extended to participants with a family history of breast, colon, esophageal, pancreas, prostate, and renal cancers after adjustment for demographic and environmental risk factors (P<.05). Conclusion: Smoking, DM, and family history may increase the risk of LGNET of various sites. Determining environmental and genetic factors related to LGNET may lead to development of surveillance and prevention strategies for high-risk individuals. No significant financial relationships to disclose.