One-third of Brazil's population, or some 58 million people, live on less than a dollar a day, a report says.
Brazil's president has promised to eliminate hunger by 2007
The "Map of Hunger" report, by the local Getulio Vargas Foundation, says poverty has increased greatly in cities over the past decade.
Brazil's President, Luiz Inacio Lula da Silva, has promised to eliminate hunger by the year 2007 when he came to power last year.
But there has already been criticism of the lack of results.
The foundation's report, released on Thursday, contained detailed information only on Rio de Janeiro, Brazil's second-biggest city.
The statistics on the drought-stricken northeastern areas, where the concentration of poor people is the largest, are due to be released later.
Their data show almost 15% of the people live below the poverty line of $27 a month in Rio de Janeiro.
The city is notorious for its slums, also known as "favelas", and high crime rates.
The average monthly salary in Rio's biggest slums was the equivalent of $140, the study showed using 2000 census data.
But in Rio's well-off districts, such as the beachside Ipanema and Copacabana, monthly wages averaged $740.
"That is really the poorest of the poor," a spokeswoman for the Getulio Vargas Foundation said.
But the BBC's former Brazil correspondent Stephen Cviic says the images of Brazilian poverty - the shanty towns, the street children, the parched landscapes of the north-eastern interior - are so familiar it is easy to forget this is not one of the world's poorest countries.
Brazil has a higher income per head than China, India and almost all of sub-Saharan Africa.
What it does have, however, is a staggering level of inequality, entrenched by decades of inflation, unemployment, unequal land ownership and a weak education system, our correspondent says.
Brazil's government of the 1990s put in place some serious anti-poverty programmes, but a decade of reform barely dented social injustice.
Our correspondent says that these days, many Brazilians are malnourished; few are actually starving.
However, the conditions on the outskirts of big cities remain grim, with youths hanging around doing nothing, an explosion in violent crime and a severely deficient police and judicial system, he adds.