This article presents a case study from the history of cardiology, namely, the development towards the acceptance of the coronary theory of angina pectoris. I show that the arguments which were considered decisive against the theory were not answered at the time the theory was accepted. I also point out that the experimental and practical success of the theory cannot be used to support the initial choice because, in the subsequent development, the field researchers became preoccupied with new questions and problems. In spite of this, there is a sense in which the field of angina research has progressed, but it remains a challenge to exactly characterise in what sense this is the case.