When Tyson Foods Inc. and Wal-Mart Stores Inc. received internalreports that employees may have paid bribes in Mexico, each facedthe same vexing question: should they turn themselves in to U.S.authorities?

Tyson, the biggest U.S. food processor, admitted bribinggovernment-employed inspectors and paid $5.2 million to avoidprosecution. Wal-Mart, the world's largest retailer, began aninternal probe in 2005, shut it down and didn't disclose the matterto regulators and prosecutors until late last year, after learningthe New York Times was investigating, the paper said.

The U.S. offers leniency to companies like Tyson thatself-report. Yet many choose to remain quiet, calculating that theywill cooperate with the government if it uncovers their bribery.Companies root out their wrongdoing and improve their complianceprograms, assuming that any credit the government gives them forself-reporting is not worth the fines and penalties and negativepublicity that follow disclosure.