: Our objective was to assess the association between smoking status before the onset of disease and inflammatory bowel disease (IBD) in Israeli Jewish patients through a case-control study conducted at the Hadassah University Hospital in Jerusalem, Israel, and a periodic health examination center. The cases included 71 patients with ulcerative colitis (UC) and 91 with Crohn's disease. Patients younger than 18 years at onset of disease were excluded. The controls included 162 healthy, asymptomatic individuals, matched with the patients with IBD by age at onset of disease and gender. Fewer patients with UC were current smokers (9.8%) than were controls (25.0%; p < 0.05). More patients with UC were former smokers (21.0%) than were controls (14.0%; p < 0.05). The odds ratio for UC in smokers compared with ex-smokers was 0.26 (95% CI, 0.13-0.53), and for smokers compared with never-smokers was 0.34 (95% CI, 0.21-0.54). No significant associations were found between smoking status and Crohn's disease. The results for UC are consistent with most reports and probably reflect a true association between smoking status and disease. The lack of association between smoking and Crohn's disease is in agreement with a previous Israeli study but differs from other reports. This may reflect a genetic predisposition among Jews that obscures the effects of smoking.