AIM: To analyze the relationship between smoking and nonalcoholic fatty liver disease (NAFLD). METHODS: This is a cross-sectional study of a healthy population, carried out in a check-up unit of a university hospital in Mexico City. We enrolled 933 subjects, 368 current smokers (cases) and 565 persons who had never smoked (controls). Demographic, metabolic and biochemical variables were measured in the two groups. NAFLD was determined by ultrasound and metabolic syndrome according to ATPⅢ. RESULTS: A total of 548 men (205 cases and 343 controls) and 337 women (114 cases and 223 controls) were included in the analysis. Statistical differences between cases and controls were observed only in high blood pressure prevalence (6.6% vs 11.3%, P<0.05; cases and controls respectively), high-density lipoproteins (1.00±0.26 vs 1.06±0.28 mmol/L, P< 0.005), triglycerides (2.18±1.49 vs 1.84±1.1 mmol/L, P<0.001), and erythrocyte sedimentation rate (11.3±9.3 vs 13.5±11.9 mm/h, P<0.001). No differences were observed in the prevalence of NAFLD (22.27% vs 29.68%, P=NS) and metabolic syndrome (41.69% vs 36.74%, P = NS). Univariate analysis showed that smoking was not a risk factor for NAFLD (OR=0.89, 95% CI 0.65-1.21). CONCLUSION: No differences in NAFLD prevalence were observed between current smokers and nonsmokers, and furthermore, no differences were observed in heavy smokers (more than 20 packs/year), indicating that there is no relationship between smoking and NAFLD. AIM: To analyze the relationship between smoking and nonalcoholic fatty liver disease (NAFLD). METHODS: This is a cross-sectional study of a healthy population, carried out in a check-up unit of a university hospital in Mexico City. We enrolled 933 Subjects, 368 current smokers (cases) and 565 persons who had never smoked (controls). Demographic, metabolic and biochemical variables were measured in the two groups. NAFLD was determined by ultrasound and metabolic syndrome according to ATP III. RESULTS: A total of 548 Statistical differences between cases and controls were observed only in high blood pressure prevalence (6.6% vs 11.3%, P <0.05; cases (114 cases and 223 controls) were included in the analysis and controls respectively, high-density lipoproteins (1.00 ± 0.26 vs 1.06 ± 0.28 mmol / L, P <0.005), triglycerides (2.18 ± 1.49 vs 1.84 ± 1.1 mmol / L, P <0.001), and erythrocyte sedimentation rate ± 9.3 vs 13.5 ± 11.9 mm / h, P <0.001). No dif ferences were observed in the prevalence of NAFLD (22.27% vs 29.68%, P = NS) and metabolic syndrome (41.69% vs 36.74%, P = , 95% CI 0.65-1.21) CONCLUSION: No differences in observed smokers and nonsmokers, and no differences were observed in heavy smokers (more than 20 packs / year), indicating that there is no relationship between smoking and NAFLD.