The Royal Society holds 14 discussion meetings a year, on frontier topics proposed by fellows and others. The HIV meeting was proposed by the late Bill Hamilton to discuss the controversial hypothesis that HIV entered the human population through trials of an oral polio vaccine (OPV). It was agreed that this would be done in a wider context, such as cross species transmission (from animals to man), virus evolution and public health.

Owing to a misunderstanding of the purpose of the meeting, and because of the dissension aroused by the hypothesis, we found it impossible to arrive at a well-balanced set of speakers in time for the meeting in May. We learned that additional data would become available in the next few months, highly relevant to the OPV controversy, including the re sults of independent blindtesting of remaining oral polio vaccine stocks, evidence on the prevalence of a related virus in chimpanzees, and major publications on evolution and rate of change of HIV. So we have postponed the meeting until September.

I refute the assertion that the postponement is "an attempt to load the dice" in favour of one of the parties to the debate. The Royal Society does not shirk from tackling important scientific issues, but we have always tried to ensure that the protagonists be fairly represented.

Sir Aaron Klug
President, The Royal Society