GlaxoSmithKline has agreed to publish results of clinical tests on its drugs, to settle a US lawsuit.
Glaxo will now publish all test results online
The firm was sued by New York attorney-general Eliot Spitzer over allegations that it withheld negative information about its antidepressant pill, Paxil.
The firm had already agreed to publish data on Paxil, also known as Seroxat.
But the deal with Mr Spitzer, which includes a $2.5m (£1.4m) payment, means the firm will publish all tests since December 2000 by the end of 2005.
The December 2000 cut-off marks the point at which Glaxo Wellcome merged with Smithkline Beecham.
Mr Spitzer has been dubbed "The Sheriff of Wall Street" for his relentless pursuit of corporate wrongdoing in the name of middle and low-income Americans.
His targets have included air polluters, Wall Street investment banks and the mutual funds in which the majority of US households have savings.
His inquiries have left a trail of financial settlements down Wall Street, as the US stock market watchdog opened its own investigations into his targets.
Nor has Mr Spitzer hesitated to take his crusades to Capitol Hill, leading to speculation that he has political ambitions of his own.
Glaxo first agreed to publish some of the data on Paxil in a "Clinical Trials Register" in June, just weeks after Mr Spitzer's lawsuit was launched.
At the time, it also agreed to publish results of tests on new drugs.
But it is now promising to put historical data - affecting drugs it currently sells - on the web as well.
Tests on new drugs will be posted within 10 months of a product's approval, Glaxo said, while future tests on existing drugs will be published within 10 months of completion.
The register will contain summaries of the results of clinical trials in a standard format, Mr Spitzer said in a statement.
In his suit, the New York attorney general said Glaxo had carried out five studies on Paxil's effects on children and young people, but had only published one.
The unpublished ones suggested a possible increased risk of suicidal thinking in some individuals, the suit alleged.
It also accused the firm of suppressing the data from its regular advice to doctors.
The case was based partly on an internal document from 1999 which said the firm wanted to "manage the dissemination of data in order to minimise any potential negative commercial impact".
Marjorie Wallace, Chief Executive of the mental health
charity Sane, said: "We are delighted that GSK have now taken the lead in making all the information from clinical trials available to doctors and the public.
"All drugs have side effects, and everyones biochemistry is different.
"This new move will enable both doctors and patients to assess the risk, benefit and choice of drugs more safely."