Background: Conceptions of medical teachers regarding learning and teaching affect their teaching practice. Therefore conceptions should be addressed in faculty development. Aim: To facilitate this, we constructed the Conceptions Of Learning and Teaching (COLT) instrument. Method: The COLT was adapted based on experts' comments during a meeting and interviews, followed by a Delphi procedure (Part I). It was administered to teachers from two Dutch medical schools with different traditions in student-centred education (Part II; N=646). The data were analyzed using confirmatory factor analysis and reliability analysis. Results: 324 Teachers (50.2%) completed the questionnaire. Confirmatory factor analysis did not confirm the underlying theoret...