1. Westland/Hallmark Meat Co. (California), 2008
The recall: 143 million pounds of beef
The problem: under investigation. Plant employees allegedly violated U.S. Department of Agriculture safety regulations by allowing "downed" cattle to be slaughtered.
2. Thorn Apple Valley Inc. (Michigan), 1999
The recall: 35 million pounds of frozen, ready-to-eat meat products
The problem: potential contamination with listeria bacteria of meat at a processing plant in Arkansas. No illnesses reported.
3. Pilgrim's Pride Corp./Wampler Foods (Pennsylvania), 2002
The recall: 27.4 million pounds of cooked turkey and chicken sandwich meat
The problem: listeria contamination. Fifty-two illnesses and seven deaths reported in the Northeast in association with the bacterial outbreak.
4. Hudson Foods Co. (Nebraska), 1997
The recall: 25 million pounds of ground beef
The problem: listeria contamination. Fewer than 20 illnesses reported. Beef supplied to fast-food retailers, including Burger King, which later dropped the company as a provider.
5. Topps Meats Co. (New Jersey), 2007
The recall: 21.7 million pounds of frozen hamburger patties
The problem: E. coli contamination. More than 30 illnesses reported in eight states.
6. ConAgra Foods (Colorado), 2002
The recall: 18.6 million pounds of beef
The problem: E. coli contamination. Thirty-four illnesses reported in 10 states.