Philip Goulder is a Wellcome Trust Senior Clinical Fellow in Oxford. He is one of the outstanding paediatric researchers in the United Kingdom. His scientific contributions are in three key areas of work. First, he has been a world leader in establishing, as a principal mechanism by which HIV can evade the immune response, the role of so-called "CTL escape.” In this way, mutations within regions of the virus that encode fragments of proteins that represent targets for recognition of virus-infected cells by the immune response result in viral escape from immune recognition. This work has clear implications in the quest for a vaccine. A second area of Dr Goulder's work has been to define the specific protein fragments that are targeted by the immune response, not only in populations in North America and Europe but now, importantly, in the populations worst affected, namely in sub-Saharan Africa. Third, he has developed novel techniques by which HIV-specific T cell activity can be readily characterised in detail in environments where less well developed laboratory facilities exist. His work has had a major impact in the field of HIV throughout the world.