This report is a first step towards building a qualitative understanding of the way illicit or criminal activities interact with the economy, security and development of West African states. Going beyond a traditional analysis of illicit financial flows (IFFs), which typically emphasises the scale of monetary flows, the report examines the nature of thirteen overlapping, and oftentimes mutually reinforcing, criminal and illicit economies, with a view to identify their resulting financial flows and development linkages. In taking this approach, this report identifies the networks and drivers that allow these criminal economies to thrive, with a particular emphasis on the actors and incentives behind them. As a conclusion to this work, this report proposes a series of policy considerations to assist countries to prioritise and focus their responses to reduce the development impacts of IFFs. Resolving the problem of IFFs requires responding to underlying development challenges, and tackling all parts of the problem in source, transit and destination countries.