Ethically, as the battle over Oxford university's controversial new bio-medical research centre has shown, it depends which side of the argument you are on. But morals aside, now we can do all sorts of clever things with cell cultures and computer simulations, do we need to use living creatures to drive medical science forwards?

The government certainly thinks so, as vivisection is still perfectly legal - if heavily regulated. "The Animals (Scientific Procedures) Act 1986 forbids the use of animals if other adequately validated methods can provide the required information," says a spokesman for the Medicines and Healthcare products Regulatory Agency, the body that licenses new medical treatments. "By the time a potential new medicine goes into the animal-testing stage of development, it has already passed through all the available non-animal methods."

Recent beneficiaries of animal testing are breast cancer patients who have been prescribed the drug Herceptin, which was developed using mice. So are more than 70% of Nobel prize winners in the fields of physiology and medicine. Nevertheless, anti-vivisection campaigners such as Andrew Tyler of Animal Aid aruge that "you can't reliably apply data obtained from animals to the sphere of human medicine. Animal experiments add only confusion."

While it is true that testing a drug, for example, on a pig, will not tell you definitively how a human will react to it, the argument is more complex. Pigs are not humans, but they are a lot closer than a dish of cells or a latex model. Gill Langley, scientific adviser to the British Union for the Abolition of Vivisection, agrees. "I would never claim that all animal experiments are without scientific value," she says, but argues that more needs to be done to develop non-animal alternatives.

A few years ago I was a doctor looking after an elderly man whose heart had been partially replaced by a metal pump developed partly in sheep. It gave him a few extra years. Living bodies - for the foreseeable future - are too complex to be universally and glibly replaced by culture dishes and simulations and, if animal testing saves lives, for now they remain absolutely necessary.