Abstract
The personality structure of 65 volunteers for a Phase 1 drug trial was examined using the Eysenck Personality Questionnaire. It revealed a common pattern of high extroversion, low neuroticism and psychoticism. The reasons why the study might attract such people are examined and the structure compared with those that take drugs that might have 'strange or dangerous effects'. The likely forms of bias that this personality structure may bring to the trial are explored.