This article interest to the intensity, even the violence of the debates, polemics and controversies around the question of colonial memory and its impact on representations, as well as the place given to migrants from former colonies reveals the extent to which colonisation and decolonisation continue to affect French society and, more broadly, Western societies. The blurring of boundaries between scientific and political debates and the resulting circulation of categories used in controversies on colonial memory, their link to migration issues, racism and discrimination phenomena, ethnic and racial inequalities, Islamic terrorism and delinquency, all reveal a confusion in issues, the polarisation of perspectives and the difficult emancipation of the scientific debate from socio-political issues. But the intensity of the conflicts around a subject that remained, until now in France, confined to a circle of militant intellectuals or specialists of the field, lecturing halls and academic publishers, can only be understood in terms of the link between the debate regarding colonial memory and the issue of ‘immigration’.