Abstract
This chapter discusses the methodological challenges in defining, operationalising and measuring organised crime infiltration in legal businesses. It first reviews existing definitions and measures of organised crime; it then focuses on infiltration, outlining the differences with respect to the concepts of organised crime investments and money laundering. It discusses the strengths and the weaknesses of existing measures and methodological approaches (e.g. analysis of statistics on confiscated assets, of personal holdings, of case studies), suggesting further directions to improve the collection of data and research in this field.