Two big US names have launched advertising campaigns to "set the record straight" about their products and corporate behaviour.
Wal-Mart is fighting allegations of low pay and discrimination
The world's biggest retailer Wal-Mart took out more than 100 full page adverts in national newspapers.
The group is trying to see off criticism over it pay deals, benefits package and promotion strategy.
Meanwhile, drugs group Eli Lilly is planning a campaign against "false" claims about its product Prozac.
Wal-Mart kicked off the battle with adverts in newspapers like the Wall Street Journal, using an open letter from company president Lee Scott saying it was time for the public to hear the "unfiltered truth".
"There are lots of 'urban legends' going around these days about Wal-Mart, but facts are facts. Wal-Mart is good for consumers, good for communities and good for the US economy," Mr Scott said in a separate statement.
Its adverts - and a new website - outlined the group's plans to create more than 10,000 US jobs in 2005.
Wal-Mart's average pay is almost twice the national minimum wage of $5.15 (£3.90) an hour, while employees are offered health and life insurance, company stock and a retirement plan, the adverts say.
Unions accuse Wal-Mart of paying staff less than its rivals do, with fewer benefits.
In California, the company is fighting opposition to new stores amid allegations it forces local competitors out of business. Lawmakers in the state are also examining allegations that the firm burdens the state with an unfair proportion of employee health care costs.
"I think they are going to have a tough time suddenly overcoming the perceptions of some people," said Larry Bevington, chairman of Save Our Community - a group fighting to prevent Wal-Mart opening a store in Rosemead, California.
Wal-Mart is also fighting two lawsuits - one accusing it of discriminating against women and another alleging it discriminates against black employees.
Meanwhile Eli Lilly is launching a series of adverts in a dozen major newspapers, to present what is says are the true facts about its anti-depressant drug Prozac.
The move is in response to a British Medical Journal article that claimed "missing" Lilly documents linked Prozac to suicide and violent behaviour.
Eli Lilly has vowed to stand up for its drug
In the averts, entitled An Open Letter from chief executive Sidney Taurel, the company says the article continues to "needlessly spread fear among patients who take Prozac".
"It was simply wrong to suggest that information on Prozac was missing, or that important research data on the benefits and possible side effects of the drug were not available to doctors and regulators," the letter added.
Eli Lilly's chief medical officer Alan Breier said that the article was "false and misleading" as the documents it referred to were actually created by officials at the US Food and Drug Administration (FDA) and presented to an FDA meeting in 1991.
Later, FDA medical advisors agreed the claims were based on faulty data and there was no increased risk of suicide.