Uuringu läbiviijate hulgast peab olema määratud uuringu juht, kes koordineerib uuringu läbiviimist uuringukeskuses ning tagab teabevahetuse Ravimiameti ja eetikakomiteega. Kui uuring toimub mitmes uuringukeskuses, tuleb igas neist määrata uuringu juht.
"Investigator": a doctor or a person following a profession agreed in the Member State for investigations because of the scientific background and the experience in patient care it requires. The investigator is responsible for the conduct of a clinical trial at a trial site. If a trial is conducted by a team of individuals at a trial site, the investigator is the leader responsible for the team and may be called the principal investigator.