OBJECTIVE: To analyze the variation in the proportion of households living below the poverty line in Brazil and the factors associated with their impoverishment. METHODS: Income and expenditure data from the Household Budget Survey, which was conducted in Brazil between 2002-2003 (n = 48,470 households) and 2008-2009 (n = 55,970 households) with a national sample, were analyzed. Two cutoff points were used to define poverty. The first cutoff is a per capita monthly income below R$100.00 in 2002-2003 and R$140.00 in 2008-2009, as recommended by the Bolsa Família Program. The second, which is proposed by the World Bank and is adjusted for purchasing power parity, defines poverty as per capita income below US$2.34 and US$3.54 per day in 2002-2003 and 2008-2009, respectively. Logistic regression was used to identify the sociodemographic factors associated with the impoverishment of households. RESULTS: After subtracting health expenditures, there was an increase in households living below the poverty line in Brazil. Using the World Bank poverty line, the increase in 2002-2003 and 2008-2009 was 2.6 percentage points (6.8%) and 2.3 percentage points (11.6%), respectively. Using the Bolsa Família Program poverty line, the increase was 1.6 (11.9%) and 1.3 (17.3%) percentage points, respectively. Expenditure on prescription drugs primarily contributed to the increase in poor households. According to the World Bank poverty line, the factors associated with impoverishment include a worse-off financial situation, a household headed by an individual with low education, the presence of children, and the absence of older adults. Using the Bolsa Família Program poverty line, the factors associated with impoverishment include a worse-off financial situation and the presence of children. CONCLUSIONS: Health expenditures play an important role in the impoverishment of segments of the Brazilian population, especially among the most disadvantaged.