It has been argued extensively that diagnostic services are a general good, but that it is offered in excess. So what is the problem? Is not “too much of a good thing wonderful”, to paraphrase Mae West? This article explores such a possibility in the field of radiological services where it is argued that more than 40% of the examinations are excessive. The question of whether radiological examinations are excessive cries for a definition of diagnostic futility. However, no such definition (...) is found in the literature. As a response, this article addresses the issue of diagnostic futility in five steps. First, it investigates whether the concept of therapeutic futility can be adapted to diagnostics. A closer analysis of the concept of therapeutic futility reveals that this will not do the trick. Second, the article scrutinizes whether there are sources for clarifying diagnostic futility in the extensive debate on excessive radiological examination. Investigating the debate’s terms and definitions reveals a disparate terminology and no clear concepts. On the contrary, the study uncovers that quite different and incompatible issues are at stake. Third, the article examines a procedural approach, which is widely used for settling controversies over utility by focusing on the role of the professionals. On scrutiny however, a procedural approach will not solve the problem in diagnostics. Fourth, a value analysis reveals how we have to decide on the negative value of excessive examinations before we can measure excess. The final and constructive part presents a definition of diagnostic futility drawing upon the lessons from the previous analytical steps. Altogether, too much radiological examination is not a good thing. This is simply because radiological examinations are not unanimously good. Excessive radiological examinations can be defined, but not by one simple general and value-neutral definition. We have to settle with contextually framed value-related definitions. Such definitions will state how bad “too much of a good thing” is and make it possible to assess how much of the bad thing there is. Hence we have to know how bad it is before we can tell how much of it there is in the world. (shrink)