"Monkey they work, baboon they chop" goes an old Nigerian saying. The people work while their leaders eat. Not Ngozi Okonjo-Iweala. Nigeria's combative Finance Minister has rolled up her sleeves since her appointment last year by President Olusegun Obasanjo. A former World Bank vice president, Okonjo-Iweala, 50, was lured back from Washington to her oil-rich yet impoverished West African nation of 130 million to fix its chaotic finances and clean up corruption. The bottom line: the Nigerian government exported $20 billion worth of oil last year, but its people still scrape by on an average wage of just a dollar a day. Okonjo-Iweala's mission is to make sure more of those billions go to roads, schools and health care.

Fixing Africa's broken giant is no easy task. Berlin-based watchdog Transparency International ranks Nigeria the second most corrupt place in the world, after Bangladesh. Oil money has often been wasted in kickbacks and bribes. The country's economy has struggled with years of mismanagement. Okonjo-Iweala, who studied at Harvard and M.I.T., has begun trimming Nigeria's bloated civil service, cut fuel subsidies and begun accounting for all the money the government spends. She has also helped set up an antifraud team to crack down on "419" letter and Internet advance-fee scams, which bilk everyone from unsuspecting pensioners to large banks by convincing them to part with their money on the promise of a cut of hidden "millions." The team has already caught more than 500 people.

Yet to hear her tell it, she's on the receiving end. "I've been very grateful for what my life has become," says Okonjo-Iweala. "My motivation is to take whatever knowledge I have and put it to the use of my country." Other ministers, who earn around $6,000 a year, initially questioned her hefty (more than $240,000) salary, paid by the United Nations in a program to repatriate Nigeria's best brains. The scam artists want to kill her, she says, because they don't like her meddling. But Okonjo-Iweala, a mother of four, can play tough too. When President Obasanjo announced he had removed the vital budget and planning departments from her ministry, Okonjo-Iweala quit, returning only when the President backed down.

Improving Nigeria's image, she says, is as important as fixing its economy. "It is a sense of anger that drives me. Anger that this country [and] the Nigerians that I know are being maligned by a small percentage," she says. "You have to do something to clean this up. You can't always look up to other people do to it. The fight begins with you." And with that, she gets back to work.