In the title of his paper Rees (2005) asked a perfectly valid question with regard to one specific element: the effectiveness of European legislation in enhancing the impact of zoo research in conservation. However, the question was not fully addressed, and the answer may be difficult to determine, due in part to the increasing importance placed on research by zoos independently, and in many cases ahead of, legislation. He discusses at some length the way in which the proportion of zoo based research has shifted in recent years to accommodate and address many of the more technically challenging issues of nutrition, reproduction and population dynamics but without losing sight of the valuable behavioural elements of research on captive animals. Rees manages during the course of his argument to answer many of his own questions, with some clear examples of where and how the practical link can be made between many zoo activities, not just research, and the ultimate delivery of conservation benefits to species. It is worth noting, however, that in many cases the truly measurable and sustainable effect of conservation action on populations, species and habitats requires a timescale that spans generations and therefore may not yet be apparent.