BACKGROUND Hepatitis B virus (HBV) infection is a major public health problem in Brazil. Several risk factors are involved in HBV infection and their identification by a rational and essential approach is required to prevent the transmission of this infection in Brazil. OBJECTIVES To evaluate risk factors associated with HBV infection in South Brazil. METHODS A total of 260 patients with HBV and 260 controls from Caxias do Sul (state of Rio Grande do Sul, Brazil) participated in this study. All participants were given a standard questionnaire to yield the sociodemographic information and to identify HBV risk factors. HBV infection was detected by HBsAg test in all participants. FINDINGS HBV infection in these cases was strongly associated with history of a family member HBV-infected, mainly mother [odds ratio (OR) = 4.86; 95% confidence intervals (CI): 1.69–13.91], father (OR = 5.28; 95% CI: 1.58–17.71), and/or siblings (OR = 22.16; 95% CI: 9.39–52.25); sharing personal objects (OR = 1.40; 95% CI: 1.37–2.38); and having history of blood transfusion (OR = 2.05; 95% CI: 1.10–2.84). CONCLUSIONS HBV infection was strongly associated with having a family member infected with hepatitis B, sharing personal objects, and having history of blood transfusion.