IF, as Sheila Brennan claims (Letters, April 25), animal research was irrelevant, then no-one would support it, and no-one would do it.

But there are ethical limits to human clinical studies - in other words, the experimentation that can be done using people. Other techniques, like tissue cultures and computer techniques, are not yet good enough to replace animal methods.

Any knowledgeable doctor will confirm that many of the major medical advances of this century (tissue transplantation, insulin, polio vaccine, antibiotics, modern anaesthetics etc) were developed through animal research. Such research continues to be vital in areas such as AIDS, cancer, cystic fibrosis, arthritis and Alzheimer's disease.

While we still need to use animals in medical research, we must make sure they are looked after properly and used in minimum numbers. The very strict controls in this country ensure that laboratory animal welfare is safeguarded in this way.

BARBARA DAVIES, Deputy Director, Research Defence Society, Great Marlborough Street, London.

Converted for the new archive on 14 July 2000. Some images and formatting may have been lost in the conversion.