The southern Gulf Coast of the United States bore the brunt of Katrina. Officials believe several thousand people may be dead.
Thousands of people have been made homeless in New Orleans. Some 80% of the city is flooded and there has been widespread looting. A complete evacuation of the city has been ordered.
The death toll in Mississippi is at least 100, while hundreds of houses and businesses - including dozens of waterfront casinos - have been destroyed. About a million homes are without electricity.
In Biloxi, one of the most seriously damaged towns, many casinos and businesses have been looted. The town of Gulfport has also been heavily damaged.
About 400,000 homes and businesses are without power in Alabama, while parts of the city of Mobile have been badly flooded.
In southern Florida, where the hurricane passed through on 25-26 August, 100,000 homes and businesses are without electricity.