AIM To identify environmental risk factors associated with the development of Crohn’s disease(CD) in order to reassess the hygiene hypothesis.METHODS A hospital-based, case-control study was carried out with CD patients(n = 145) and controls(n = 163)representing a socioeconomically diverse statewide catchment area in Brazil. Controls were recruited from caregivers of patients seen in different outpatient clinics at the same hospital. A multi-item survey with 94 questions regarding family history of CD, perinatal and childhood circumstances, living conditions, tobacco use and familial socioeconomic status was carried out by interviewers. RESULTS On the univariate analysis, predictive variables for CD included being male, under age of 40, a high education level, urban dweller, smaller family size, exposure to enteric pathogens and user of treated water(P < 0.005). On the multivariate analysis, variables significantly associated with CD were male gender(OR = 2.09), under age 40(OR = 3.10), white(OR = 2.32), from a small family in childhood(OR = 2.34) and adulthood(OR = 3.02), absence of viral infections in childhood(OR = 2.23), exposure to enteric pathogens(OR = 2.41), having had an appendectomy(OR = 2.47) and prior or current smoker(OR = 2.83/1.12). CONCLUSION Most variables supporting the “hygiene hypothesis” are associated with the development of CD but are not independent predictors of the diagnosis. AIM To identify environmental risk factors associated with the development of Crohn’s disease (CD) in order to reassess the hygiene hypothesis. METHHODS A hospital-based, case-control study was carried out with CD patients (n = 145) and controls (n = 163) representing a socioeconomically diverse statewide catchment area in Brazil. Controls were recruited from caregivers of patients seen in different outpatient clinics at the same hospital. A multi-item survey with 94 questions regarding family history of CD, perinatal and childhood circumstances, living conditions results on tobacco use and familial socioeconomic status were carried out by interviewers. RESULTS On the univariate analysis, predictive variables for CD included being male, under age of 40, a high education level, urban dweller, smaller family size, exposure to enteric pathogens and user of treated water (P <0.005). On the multivariate analysis, variables significantly associated with CD were male gender (OR = 2.09), under age 40 (OR = 3.10) (OR = 2.32), from a small family in childhood (OR = 2.34) and adulthood (OR = 3.02), absence of viral infections in childhood Had an appendectomy (OR = 2.47) and prior or current smoker (OR = 2.83 / 1.12). CONCLUSION Most variables supporting the “hygiene hypothesis ” are associated with the development of CD but are not independent predictors of the diagnosis.