There have been numerous references to complexity theory and complex systems in the recent healthcare literature, including nursing. However, exaggerated claims have (in my view) been made about how they can be applied to health service delivery, and there is a widespread tendency to misunderstand some of the concepts associated with complexity thinking (usually justified by describing the misconception as a metaphor). These concepts can be extended to systems and structures in healthcare organisations but, at this stage in the development of complexity science, only in a modest and very cautious way. In this paper I first outline some of the key ideas in the theory of complex adaptive systems, and then suggest that they have been distorted by a series of influential articles in the medical literature. I go on to present a simple case study of my own and undertake a complexity analysis of it. In the conclusion I suggest that we should beware of some outdated ideas being trotted out in the guise of complexity - an exciting and diverse area of enquiry that those old ideas do not, in fact, resemble.