1 INTRODUCTION Research by design is a new phenomenon in the sci- entific field of many architecture schools. Evidence of this can be seen in the large number of conferences, publications on research by design but also in the gen- eral use of the concept in public and private commis- sions (e.g. investigations commissioned by various Belgian Bouwmeesters). Yet, if the concept is very popular, it is often used very loosely, as if all assump- tions around its meaning and its methods were com- monly shared. There tend to be two main confusions regarding the definition of research by design. On one hand, many scholars are prone to declare that ordinary ar- chitectural design is research in itself. Yet, there are major differences between a regular architectural pro- ject and research by design in terms of produced knowledge, method, systematics, validation by peer- reviewing, or reproducibility (Archer, 1979). On the other hand, studies commissioned by public or private sponsors are also often stamped under the label re- search by design. Yet again, most of the time, those studies do not qualify for such a definition for the rea- sons stated above in the case of architectural projects. In order to clarify matters, this paper tries to shed light on the major differences between study and re- search by design. To this end, a recent study on the European Quarter of Brussels will be used as a pretext for questioning the relationship between the two con- cepts. This paper is organized into four sub-sections. Firstly, the scope of a study carried out in the Euro- pean Quarter of Brussels is exposed in terms of mis- sion statement, stakeholders and findings. Secondly, the general definition of the concepts of research by design and study are considered. Thirdly, the differ- ences between the concepts are brought to light through the example of the European Quarter study. Finally, the differences, as well as the commonalities, are summarized in a general conclusion. 2 PRETEXT: A REGULAR STUDY 2.1 Mission statement The work that serves as a pretext for bringing to light the differences between research by design and study is a regular study that was carried out in Brussels. The aim of this investigation was to apprehend the resi- dential attractiveness of a particular district, the Eu- ropean Quarter, and its possible levers for improve- ment. This ambition could be summarized as an at- tempt to transform the district into a neighbourhood. 2.2 Stakeholders The investigation was commissioned in 2015 by a semi-public organization, the King Baudouin Foun- dation. The goal of this independent foundation is to improve living conditions for the population in Bel- gium. The European Quarter of Brussels: From District to Neighbourhood The difference between Study and Research by Design G. Ledent Université catholique de Louvain, Brussels, Belgium J.-P. De Visscher Université catholique de Louvain, Brussels, Belgium ABSTRACT: Two kinds of investigations are usually carried out in the discipline of architecture: research by design and study. They are often mistaken for one another and the current trend is to call the latter research by design even though it does not technically qualify for it. In order to illustrate the differences between the two kinds of investigations, a similar question is addressed by means of the two notions. This question relates to the issue of the residential attractiveness of the European District of Brussels for which a genuine study was carried out in 2015. This analysis demonstrates major discrepancies between study and research by design in terms of framework, generalization, reproducibility and falsification. Yet, beyond those differences, both investigations could be valuable for one another if they were recognized for what they are.