South Africa's high court is hearing a challenge by 40 big pharmaceutical companies, including three Swiss firms, against a government law allowing the importation of cut-price drugs.
The lawsuit is centred on a South African law adopted in 1997 - but never implemented - which gives the health minister a limited right to import generic versions of patented drugs or licence their domestic production.
An alliance of drug companies - including Switzerland's Roche, Novartis and Janssen-Cilag - is arguing that the law infringes the companies' patent rights. It says that by granting the health minister these "excessive powers" the law discriminates against the industry, endangering profits and future research.
The case has stirred up emotions in a country, which is struggling with an Aids epidemic. According to the United Nations, South Africa has the highest HIV infection rate in the world, with about 10 per cent of its 45 million people afflicted.
The government maintains that at present it cannot afford the drugs that are desperately needed for fighting Aids and other diseases. It argues that it can best ensure that everyone has access to healthcare by allowing imports of cheap versions of well-known drugs.
But the industry fears that if cut-price drugs become widely available in developing countries they could also filter through to the West.
It points out that South Africa has hitherto refused to distribute Aids medication to its people, even a relatively inexpensive but effective course of anti-retroviral medication.
It also accuses the government of declining pharmaceutical companies' recent offers of Aids drugs at vastly reduced prices.
For its part, the government says that even at reduced prices the quantity of drugs needed would bankrupt its health budget.
The stalemate has been going on for three years and appears likely to drag on for some time to come.
"We're dealing with a very enormous challenge and success is not going to be easy," the health ministry director general, Ayanti Ntsaluba, said.
swissinfo with agencies