CDISC-Gloss – A person responsible for the conduct of the clinical trial at a trial site. If a trial is conducted by a team of individuals at a trial site, the investigator is the responsible leader of the team and may be called the principal investigator. [ICH E6 1.35. 2.] See also investigator, coordinating investigator, investigator/institution, principal investigator, sponsor-investigator, sub-investigator.